sal role service and role injection

sal role service and role injection

role cannot be assigned to the whole of openflowplugin.
Since we are scaling switches across a cluster, the role would be assigned per device.

Added a new sal-role yang, rpc and service.

This would be the first of subsequent commits.

Made changes to merge to master - header and testchanges

Change-Id: I0a681485c5ccb8bc839b3b18f3efb648b88bd86b
Signed-off-by: Kamal Rameshan <kramesha@cisco.com>
(cherry picked from commit f6d2398e08b0a9b2d7bb5c533e9ca17a5041a74f)