Unit aggregation and selection of unit approximations seem to be broken

There has been an update to the logic of unit aggregation (commit 942c77f0). Somehow, the behaviour was earlier and is now different for different users, i.e., whether for example level3 in unitUnitEffLevel means the start of level3 or the start of level4. The reason is unclear. In addition, the situations when the user wants to start the simulation with aggregated units should be better handled.