Per conversation options.

Added per conversation options. Right now the only options for each
conversation is custom notification ringtone, vibration settings.

This is useful as for each thread, you can have a custom ringtone.

The implementation is done with a custom database. This is ideal as we
don't want to modify sqlite database from google as if they upgrade, we
will run into a lot of trouble.

Change-Id: I8e8e533cdcda14b3bc6adea0bb0db04cfbf0ce2b