Rather than storing demands at the TimeSliceID level, which requires some hacky steps to split up demands for seasonally balanced commodities then add then together again, we should store demands at the TimeSliceSelection level
I had a go at this in #1329, and pretty much got it all working, but closed that as it's now got a lot of merge conflicts, so easier to start again
Rather than storing demands at the
TimeSliceIDlevel, which requires some hacky steps to split up demands for seasonally balanced commodities then add then together again, we should store demands at theTimeSliceSelectionlevelI had a go at this in #1329, and pretty much got it all working, but closed that as it's now got a lot of merge conflicts, so easier to start again