Allow to get reservoir volume and diverted flows as controlled and/or measured variables

The Y parameter used in CreateController for getting data from the model for the supervision can currently only be used for retrieving the simulated flow Qsim_m3 of a node.

In order to be able to retrieve other data as Vsim, or Qdiv_m3, we can use the same notation as for a list node_id$variable:

• node_id or node_id$Qsim retrieves simulated flow in the river
• node_id$Vsim the volume of the reservoir
• node_id$Qdiv the diverted flow of the node

This notation should also be used for the issue #161 (closed)