Hiding neutron Client class

* This needed to introduce client() method to keep consistency with
  other OS client services already placed in Savanna
* Renamed old Client class to NeutronClientRemoteWrapper
* This is needed to fix bug #1277501

Change-Id: I346613d04143ad4a4ce58b9d6de3d464d3cd36ff
Added networks validation

* 'floating-ip-pool' field is validated on existence
* 'neutron-management-network' is validated on existence
* Added unit-tests

Change-Id: Ia4cd4b5029cb2d5d3b3cc94336fa94b849e6ef15
Closes-Bug: #1282027
Merge "Added networks validation"
Merge "Hiding neutron Client class"