Extends datastore capability overrides and adds management cmds

Added trove management commands for adding and removing capabilities and
capabily overrrides.  Relocated capability-related test setup/teardown
from TestDatastoreBase into TestCapabilities class.

Change-Id: I997ef248ef2b9e42ff0c35efea4dca737c41e84f
Partially-Implements: blueprint capabilities
micro

Change-Id: Id0874efc0cd4cd54e5eaed3cb8ec117d3e2e2f14