New Features for Blocked Contacts

1. Added a new table in database for blocked contacts
2. Bocked contacts list in setting now make use of previous database.
3. When seeing the profile of a blocked contact, now appear the option to "unblock" it instead of "block" one.
4. Added support for more than 200 blocked contact (not tested as I don't have so many blocked contacts).
5. When blocking/unblocking a contact, de table in database is updated and a notification posted (also when loading MessagesActivity.java).
6. In Contact Profile Activity, the menu bar is forced to be created/modified by the UIthread (to avoid problems when need to be modified)
7. Added comment to the methods I have added.