Increased list of fields that are verified
Moved _monitor_message and _compute_update_message code and
tests to MonitorNotification and ComputeUpdateNotification
- Converted migration to South data migration
- Made a few changes to data migration migration error reporting
- Changed the way exists were being updated
- Removed ComputeUpdateInstanceNotification
- Ensured that exists events are considered when populating rawdata
but not while populating instanceusages
Merge pull request #132 from anujm/F215-B

Incorporated Review comments/misc other changes