Tagging another pre-release

Tagging v0.3.90, a preview release for the upcoming feature-based one

Tagging v0.3, a new major release of Trojita

Summary of changes since v0.2.9.4:

- Drastic reduction in memory usage
- Tagging e-mails (contributed by Shanti Bouchez)
- Faster fetching of data
- Much more efficient support for threading
- More robust IMAP support
- A new Debug menu
- Autocompletion of e-mail addresses (contributed by Thomas Gahr)
- Reporting server/client configuration through ID
- Support of multipart/related for full rfc2387 compliance
- Showing Trojita's homepage on start
- GUI fixes (now finally works in dark themes)
- SMTP works over SSL (contributed by Shanti Bouchez)
- Expanded unit test coverage
- Plenty of bugfixes and further improvements

Tagging v0.2.9.4, a bugfix release.

Changes since v0.2.9.3:

- huge number of stability improvements
- improved logging
- changed on-disk cache format, (one-way) migration shall happen automatically

Tagging v0.2.9.3, a bugfix release.

Changes since v0.2.9.2:

- Mailboxes with recent messages now get a visual indication
- Threading is enabled again and its effectivity was improved in the process
- Drag and drop of messages between folders works again
- Threads containing unread messages are now highlighted in the GUI
- An icon and a.desktop file is now installed by default
- Some GUI tweaks
- More unit tests
- Bug fixes in IMAP code and around
- Improvements for multipart messages
- Some internal refactoring
- The IMAP parser got relaxed to accept more whitespace in server's responses

Tagging v0.2.9.2, a maintenance release.

Warning: support for threading has been temporarily disabled; it needs more work when UIDs change rapidly.

Significant changes since v0.2.9.1:
- Bugfix: handle rapid sequence of new message arrivals and expunges
- Bugfix: take care not to skip pending requests for downloading message parts
- Better UIDNEXT guessing
- Increased unit tests coverage
- XtConnect: fix issues with "stuck messages"

Tagging 0.2.9.1, an incremental bugfix over the 0.2.9.

Significant changes:

- BODYSTRUCTURE parsing made much more relaxed for GMail
- Build fixes for VS2008
- XtConnect: cache issues
- XtConnect: visual indicators on MacOSX
- Connection progress logging

Tagging v0.2.9, a beta version for 0.3

Tagging the 0.2

We should really have a "version" or something. Let's take current state and make it "0.1", then.