Implemented state caching.
FEATURE: Photos selection now would be stored in database.
FEATURE: favorite users.

Misc changes and cleanups.
Rename menu.
Reworked already existed tasks.
Added task for loading marked photos from database.
Allowed photo to have null user.
FIX: if you quickly select users to show his data - application crush follows. Added removal of delayed runnable (UserPhotosFragment.SetupRunnable), so it won't bother fragment after it's removal.
FIX: fast creation/canceling tasks caused NPE.
FIX: finally get rid of activity leak. Stress-test passed very well.
Refactored GFX.
Added menu actions to start CollageActivity.
CollageActivity right now will do only necessary work: loading checked images from database.
More work to do!