python-troveclient clustering framework refactoring

python-troveclient clustering framework refactoring

Modify existing:

trove create -----> trove instance-create

Propose new:
Taking into account different clusterable datastores we need to find 
proper way to send valid actions at the same time
(for mongodb - "add_shard", for cassandra - "add_node", etc.)

     Options:
                  trove cluster-scaleup <cluster_id> <action>
         Example:
                  trove cluster-scaleup UUID add_shard
         Pros:
                  Generic framework.
         Cons:
                  Need to know if action is valid.
                  API should raise exception is given action is not valid for cluster datastore type.


                  trove <datastore>-cluster-<action> <cluster_id>
         Example:
                  trove mongodb-cluster-add-shard UUID
                  trove cassandra-cluster-add-node UUID
         Pros:
                  Generic framework.
                  Client sets proper action.
         Cons:
                  API should raise exception is given action is not valid for cluster datastore type.