Access profiles in the create state

[rouille]

As for the Grid object, we would like to access the profiles in the building phase a scenario.

Implement the get_demand, get_hydro, get_solar and get_wind methods in the Create class. The profiles must be transformed according to changes enclosed in the change table. Every time one of these methods is called the corresponding base profile will be transformed following the changes currently enclosed in the change table. This means that the demand base profile will be returned If there is no demand key in the change table. The same applies for renewable resources.