BUG-1281: use SchemaContext lookups

SchemaContext provides efficient module lookup services. Use those
instead of homegrown versions.

Change-Id: I4406438b137c8742a5265036f84a66d7f0f441c0
Signed-off-by: Robert Varga <rovarga@cisco.com>
BUG-1281: share filters between instances

The filters are invariants, so lets share them accross instances and not
instantiate them each time we need them.

Change-Id: Ib632efe758c22bd782fca0536c2fe7e9c6e831c3
Signed-off-by: Robert Varga <rovarga@cisco.com>
Merge "BUG-1281: use SchemaContext lookups"
Merge "BUG-1281: share filters between instances"