Another little fix for #35010. Added better labeling for node groups, so it's possible to see which node group type the sockets in the node tree view belong to. Otherwise would be virtually impossible to use it.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@56247 954f8c5b-7b00-dc11-b283-0030488c597c