Electrolyser (and fuelcell?) management class setup

[AteZenmo]

We have HeatingManagement, batteryManagement, ChargingManagement, I would like to add electrolyserManagement to that list.

1. This would remove the remaining different code on GCConversion -> making that agent basically the same as the generic GC as well.
2. This would make it very easy to add electrolysers to other gc types, like companies.

Maybe the same should be done for a fuelcell.

-> And what about other 'electricity' generators? Maybe we should think this through, and maybe we can think off a management that works for more than alone a fuelcell. (Methane,diesel generators for example).