Add the possibility to save a copy of the document with the changes to it (only for form fields at the moment).

On the Document/Generator side, introduce a proper interface for the purpouse.

On the GUI side, add a new "Save As" function that save the changed document to a location.
The action is enabled only if the current backend can provide the functionality.

svn path=/trunk/KDE/kdegraphics/okular/; revision=784661