Split services code out of Neutron, pass 1

- After l3_agent is refactored, need to remove services/firewall
- After vmware plugin moves services out of monolothic,
  remove model copies and services/loadbalancer/constants,
  and re-enable unit tests.
- After alembic chain gets split in four, tweak models/head and
  fix heal/current chain.
- Re-factor test_routerserviceinsertion into one of the service repos

Partially-Implements: blueprint services-split
Change-Id: I5466984a9e57128266f97e9bd5c265f4dc3cba7b
Merge "Split services code out of Neutron, pass 1"