Critical Bug fixes and Enhacements

- Added javadoc to many methods
- Introduced wrappers around datastore API. These wrappers take care of retries, logging,
  check whether transaction is in progress, etc
- Added more tests to Python dcloud regression. Now it checks for operational state
  correctness as well
- As much as possible changed most methods to use new datastore wrappers.
- Introduced rest:uti to SF Yang. This will allow python agent to manage SFs
- Removed dead code
- Fixed several conditions where operational state was not cleared after delete
- Fixed several concurrency issues
- Fixed SFcDataStore callback to take into account transactions in progress
- Fixed logging in multiple places
- Added more documentation to Python SFC agent and SFF thread

Change-Id: If90a0c45ed928b59a5f4634c18ed2819c6723c59
Signed-off-by: Reinaldo Penno <rapenno@gmail.com>