Fix holding write lock while calling notify in legacy API
Fix write_lock being help on db when postimport plugins are run
TXT Input: Allow shipped markdown extensions to be selected and used.
Add basic debug info to unhandled error dialog
Add a tweak to debug newdb locking issues
TXT Input: Add support for markdown extensions

TXT Input: Allow using various markdown extensions for more features
when converting markdown formatted txt files. See
http://pythonhosted.org/Markdown/extensions/index.html for details.

Merge branch 'markdown_extensions' of https://github.com/user-none/calibre
Fix book count in tooltip of choose library button not updating

Fixes #1208217 [library toolbar button not updated on book deletion](https://bugs.launchpad.net/calibre/+bug/1208217)
Do not popup an error dialog for invalid message

Do not popup an error dialog when an invalid message is received from
another instance, unless we are in DEBUG mode. See #1207947
Allow refering to bugs without closing them in commit messages
...
Auto-run .ui file compilation on branch change
Conversion: Fix removal of empty inline tags

Conversion: Fix empty inline tags that are the second child of a
paragraph causing text change location. Fixes #1207735 [Conversion issue from epub to mobi.  Italicized word sometimes moves to end of paragrah.](https://bugs.launchpad.net/calibre/+bug/1207735)
Start work on cover grid
Shortcut for grid view
Wire up the grid view button
Grid view renders
Register cover caches with the db
Remember grid view state
Sync the main and grid views
Document shortcut for toggling grid view