Major rework of gRPC handling (do not merge yet)

Includes the following chages:

* Refactored proto files
  - separation of logical devices vs devices
  - common flow related message types moved to openflow_13
  - most RPC is defined in voltha.proto now
* Expanded RPC definitions to cover now most of what we
  need (a few device provisioning RPCs are still missing)
* Reworked RPC handlers to work with new config tree
* Implemented test cases for all existing RPCs, tested via
  chameleon's REST service
* Did away wih the OrderedDict internal representation
  in the config nodes (3x performance boost on bulk
  add, and negligible penalty in other ops)
* Refactored transacton merge handling to align with
  new structures

Change-Id: I3740ec13b8296943b307782e86e6b596af78140e
2 files changed