Add possibility to set which parameters use forecasts

If forecasts are used in a model currently, there has to be data for all forecasts in all time series parameters (ts_influx, ts_cf etc.). In some cases, there might only be forecast data available for some of the parameters and for others only realized values are used. For example: Hydro inflows can be assumed to be constant in the short-term, but the user might want to use forecasts for wind power, and to make the simulation work, realised inflow data needs to be copied to all forecast branches. This will become even more problematic if there are already other data for the central forecast of inflows, e.g. long-term averages, which will be used for the long-term scenarios. This central forecast data would be overwritten by the copying.