Enhancing TTP Model and Tests

We now have all the top-level slugs modeled except for flow_tables which is in
progress. We also have at least some testing for all top-level slugs except for
flow_tables and packet_out. We have yet to test packet_out becuase the spec
gives no examples and is possibly ambigous.

Change-Id: I11cb61438b4411414c77955a4bfb1313445b2440
Signed-off-by: Colin Dixon <colin@colindixon.com>