We need to be able to express a full control loop definition in TOSCA.

There needs to be:

1. A TOSCA Node Type for Control Loops
2. A TOSCA Node Type for Control Loop Elements
3. A TOSCA Node Type for Participants
4. A way of defining Control loops as a set of node templates in a topology template that uses connected node templates of the types in 1, 2 ,3 above.