BUG-1274 OF issue with datapath-id

- replaced Long with BigInteger in order to capture value greater then maxLong
- added unit test for that

Change-Id: I17d8b0c54c5c084d428883f33aa0972e3dd986ed
Signed-off-by: Michal Rehak <mirehak@cisco.com>
Merge "BUG-1274 OF issue with datapath-id"