Make heating and electricity forms only visible to group representatives

[veitu]

There was feedback that it would make sense that only the group representative can see the forms for heating and electricity - and enter the data. Because it should only be entered once for each group by the group representative.

[codingfabi]

This was already reported in #306. I create a fix for this which is just not yet deployed on the test instance.

Closing this issue as a duplicate.