LDEV-1257: Added support for Groups to be created in authoring (so that the names can be entered) and the mapping table to map groups to a sequence activity (ala branch) for a Group based branching activity.
LDEV-1229: Add a unique key on the activity columns in transition. Somehow we are ending up with duplicate rows in the database, which stops the design being opened. This will stop the bad data being written to the database.