Center folders without status (e.g. outbox) in folder list again.
Fix message list item background color
Fix and vastly simplify the query for the threaded message list

This requires another database schema change. With this change messages
at the root of a thread reference themselves in the 'threads' table,
i.e. 'root' contains the value of 'id' for these messages. It makes
selecting all messages in a thread much simpler.
Change style for button bar in setup (Android 3+)

Use the button bar layout from Roman Nurik's WizardPager example:
https://code.google.com/p/romannurik-code/source/browse/misc/wizardpager
Use theme-specific image for 'add contact' button