Add most of vtep model classes, inserts, test

The main entities, and insert methods for each in the
ConfigurationService. Untested.

Also a vteptest method in the ConfigurationService to try and execute some of
the inserts.

Change-Id: Ica3dfcc16f4f5c8f2011c565221fa9781bf9bee2
Signed-off-by: Galo Navarro <galo@midokura.com>