Add NIC bonding support in Nailgun

* Add a NodeBondInterface DB model.
* Add a new model rendering to the api/nodes/x/interfaces
  handler.
* Allow a bond creation via the handler.
* Add a data propagation to the deployment_serializer.
* Add Enum usage.
* Migration rules fixed.
* Tests fixed.
* Nets-to-NICs default assignment fixed.

TODO:
* New tests will be added soon.
* Add a lot of checks and validations.
* NodeNICCollectionhandler has an outdated behavior.
  Lets syncronize it with NodeNic handler.
* Bonding must be allowed to the nodes in cluster only.
* Bonding is not available in NovaNetwork.

Implements: blueprint nics-bonding-enabled-from-ui

Change-Id: Ib70bbe9fe897a07f2b7b201944333f70986bbb35
Merge "Add NIC bonding support in Nailgun"