Add a dam module with the lumped GR models

Following the PhD thesis of Jean-Luc Payan and the work of Morgane Terrier, we have pieces of airGR codes that allow to take into account the impact of dams in the GR4J and GR5J models. Knowing a time series of delta V, i.e. the variation of the volume of water in a dam, it is possible to subtract water from the production store and to release in the the routing store. Not sure about GR6J, Morgane told me it caused issues with the exponential store, to be checked with @charles.perrin .

Eventual inclusion of this module in airGR should be thought of considering parallel works on semi-distribution.

Also important will be how to deal with this additional input data (observed delta V time series).