Version 0.3.1:

* Added a new class ServiceConstants to SocialContract for providing constant values. Fixes #11. Fixes #16. Fixes #14.
* Updated javadoc to specify access mode, default values, DB type and constraints for all properties. Fixes #19. Fixes #15.
* Moved GLOBAL_ID, CREATION_DATE and LAST_MODIFIED_DATE to SyncColumns interface so now it is inherited by all sync-able classes. This eliminates repetitive documentation.
* Moved _ID to DBColumns interface. This eliminates repetitive documentation.
* Added _ID_PEOPLE