Inconsistent multi-period weighting for the primary energy limit global constraint

[coroa]

Checklist

• I am using the current master branch or the latest release. Please indicate:

Describe the Bug

I just realized that the primary energy limit global constraints apply the number of years each period on-top of the regular generator snapshot weightings, but only for generators. And not for storage_units/stores.

ie. for generators the underlying assumption is that the dispatch repeats in each year of the investment period and therefore needs to be counted multiple times, while for storage units and stores only the difference between the last and the first level is counted without any weighting, which is inconsistent.

I had originally expected that the primary energy limit for a particular investment period would bound the yearly emissions, but i must admit the period weighting is necessary for an overall budget, then it is also necessary for a non-cyclic store/storage unit though.

@lisazeyen @FabianHofmann