Allow assigning of Testgroups in Instancegroups
It should be possible to assign testgroups or tests to instancegroups. All instances which are a member of this instancegroup should have the selected testgroups as children in the nodetree afterwards.
We planned this on the start but dropped it in favour of a simple, straight forward implementation. The implementation became quite simple after the last changes in the node repository which made sure that whenever a node is instantiated all parent nodes from the instance to root are loaded. I mostly need feedback weather the feature is welcome or not.