This implements single-layer and multi-layer Photoshop
version 1 file export for Krita.

Squashed commit of the following:

commit 7849fd4a
Merge: 7374c20b 06577f1a
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Tue Dec 4 11:50:13 2012 +0100

    Merge branch 'master' into krita-psd_export-rempt

commit 7374c20b
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Tue Dec 4 11:39:43 2012 +0100

    Fix saving of multiline psd files

    We needed the empty global layer mask info block... Also, Qt' QRect
    bottom != photoshop's idea of a bottom.

commit 2ed3a9f7
Merge: 441c0bc9 a1f365ea
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Mon Dec 3 15:27:51 2012 +0100

    Merge branch 'master' into krita-psd_export-rempt

commit 441c0bc9
Merge: 1119bac1 13036ac6
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Sat Dec 1 10:06:24 2012 +0100

    Merge branch 'master' into krita-psd_export-rempt

commit 1119bac1
Merge: b1fa0a15 81b50cab
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Sat Nov 24 12:28:12 2012 +0100

    Merge branch 'master' into krita-psd_export-rempt

commit b1fa0a15
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Sat Nov 24 12:26:31 2012 +0100

    Do not swap top and left... Fixes saving to psd with layers

    This makes it possible for krita to load psd files it saved, but the psd
    files still are not correct, gimp cannot load them and krita complains.

commit 9a6f59e3
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Sat Nov 24 11:21:03 2012 +0100

    at least the first layer now saves correctly, no idea why the other layers are broken

commit e14d0029
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Fri Nov 23 14:31:01 2012 +0100

    Revert "don't try to create the color from itself"

    This reverts commit 348e8c20.

commit 0db1406b
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Fri Nov 23 11:49:12 2012 +0100

    fix reading of pascal strings again

commit 3fca5f7b
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Fri Nov 23 10:37:52 2012 +0100

    add unittest for compression

commit cf5b7ba8
Merge: c654ae18 a96e6ece
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Thu Nov 22 13:37:11 2012 +0100

    Merge branch 'master' into krita-psd_export-rempt

commit c654ae18
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Thu Nov 22 13:36:58 2012 +0100

    add tests for compression

commit 7b58b94c
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Thu Nov 22 12:39:16 2012 +0100

    reinstate the unittests

commit 5ef9f432
Merge: 78491ffa 368440f1
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Thu Nov 22 11:09:57 2012 +0100

    Merge branch 'master' into krita-psd_export-rempt

commit 78491ffa
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Thu Nov 22 11:09:54 2012 +0100

    ...

commit 6326e1f5
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Thu Nov 22 11:09:36 2012 +0100

    Initialize all variables

commit 348e8c20
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Thu Nov 22 10:55:30 2012 +0100

    don't try to create the color from itself

commit 3b999307
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Thu Nov 22 10:55:12 2012 +0100

    initialize variable

commit 96da561f
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Thu Nov 22 10:54:40 2012 +0100

    don't copy the same memory range over itself

commit 9efa3c37
Merge: ddf8a8cf 3eb3fdf7
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Mon Nov 19 11:00:54 2012 +0100

    Merge branch 'master' into krita-psd_export-rempt

commit ddf8a8cf
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Mon Nov 19 11:00:52 2012 +0100

    some more layer hackery

commit 5fcf27c4
Merge: b419049b e07ccbb4
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Wed Nov 14 11:31:15 2012 +0100

    Merge branch 'master' into krita-psd_export-rempt

commit b419049b
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Mon Nov 12 14:23:14 2012 +0100

    our layers are in the right order for psd

commit a41448d3
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Mon Nov 12 12:03:04 2012 +0100

    make number of layers negative, since we always have alpha in krita

commit 517940f4
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Mon Nov 12 11:05:16 2012 +0100

    implement saving of layer data (still a bit broken)

commit 3553d615
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Mon Nov 12 10:05:40 2012 +0100

    Write the layer description records

commit f5fc2faa
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Sun Nov 11 13:10:39 2012 +0100

    Correctly save rle-encoded image data

    For now, krita only saves using RLE, not uncompressed or zipped. We
    first need to save the channel lengths in a block, then the channel
    data.

commit 23d91520
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Sun Nov 11 13:10:36 2012 +0100

    write the icc resource block correctly

commit b7c0888d
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Sun Nov 11 12:52:11 2012 +0100

    when compressing, compress, don't uncompress

commit c344d565
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Sun Nov 11 12:42:41 2012 +0100

    Write the image data section

commit 9519207e
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Sun Nov 11 12:42:10 2012 +0100

    Correctly write the resource block

commit 87a8b2c9
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Sun Nov 11 11:59:48 2012 +0100

    conform to coding style

commit ac05c1b0
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Sun Nov 11 11:41:08 2012 +0100

    swap parameters to make api consistent

commit a5d2534c
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Sun Nov 11 11:40:50 2012 +0100

    start implementing packbits writing

commit 6c542e43
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Sat Nov 10 11:51:37 2012 +0100

    Load and save the icc profile

commit bb4b031e
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Fri Nov 9 17:26:18 2012 +0100

    Write the resource section

commit 8a32125a
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Fri Nov 9 17:19:15 2012 +0100

    implement writing of the colormode block

commit b702c06f
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Fri Nov 9 15:49:56 2012 +0100

    we only save version 1 psd, not psb

commit e4f434dc
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Fri Nov 9 15:46:17 2012 +0100

    Clean up psd image builder

commit aba7085b
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Tue Nov 6 10:46:55 2012 +0100

    Distinguish between different filter errors

    CreationError was used in four cases:

    * couldn't create the filter plugin
    * couldn't create the output document
    * couldn't cast KoDocument to KisDoc2
    * couldn't download the remote file

    So to avoid confusion, distinguish between these cases, and even more,
    distinguish between the case when the filter entry is inexplicably null
    and the case the filter plugin couldn't be instantiated.

commit 58ab418e
Merge: 3a6369e1 f2bb2584
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Fri Nov 9 15:25:24 2012 +0100

    Merge remote-tracking branch 'origin/master' into krita-psd_export-rempt

commit 3a6369e1
Merge: 65e21ce7 33302e6f
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Fri Nov 9 14:23:17 2012 +0100

    Merge branch 'master' into krita-psd_export-rempt

commit 65e21ce7
Merge: fa84a953 bf7d2fbc
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Thu Jul 26 10:12:31 2012 +0200

    Merge branch 'master' into krita-psd_export-rempt

commit fa84a953
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Thu Jul 12 10:44:00 2012 +0200

    Save the psd header correctly

commit 9b9c2c69
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Wed Jul 11 16:55:48 2012 +0200

    start saving the psd file

commit b8d49667
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Wed Jul 11 16:55:37 2012 +0200

    fix some warnings

commit 373be216
Author: Boudewijn Rempt <boud@valdyas.org>
Date:   Wed Jul 11 16:26:32 2012 +0200

    Re-enable the installation of the psd export filter