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
Speed up cover rendering by caching QPixmaps
Scroll per pixel
Add context menu to grid view
Double click to read in grid view
Add sorting to grid view context menu
Drag 'n drop for the grid view

Refactor the D'nD code from the main view so that it can be re-used for
the grid view directly.
Port preserve_view_state to work with the grid view
pep8
Make the cover grid customizable
Ensure that QPixmap objects are never deleted on non-GUI threads
Animate double clicks in the grid view
D'nD fixes

Fix dragging a single book in the book list using the multi-book icon.
Also use a class decorator for the API, looks nicer :)