Decoupling of SFF and SF. More bug fixes

- Decoupling SFF and SF in a upcoming commit. Today when you create
  a SF, we create a SFF if it does not exist. But any coupling
  between the models is really bad because it makes us have to do
  garbage collection and synching of data. So, the user will have
  to explicitly create a SFF and in its configuration also specify
  the list of SFs attached to it.
- Changed sfc_provider_config.json to pretty format.
- Changed SFC chain model to allow symmetric paths
- Fixed a few Yang modules with lines larger than 70 chars.
- Fixed a few Yang descriptions according to new arch draft-01
- Fixed LOG statement in SnDataListener()
- Fixed service-function-forwarders.json to use new model syntax.
- Fixed OVS yang namespace issue

Change-Id: I56227cd8ef1d8a78386c75f3c3b6fcd97f34c1cc
Signed-off-by: Reinaldo Penno <rapenno@gmail.com>