Also added code for favoriting groups, but this currently isn't enabled work since header widgets suffer from the same problem as custom widget rows do - their SWidget is created in place rather than through a function call, so thus cannot be duplicated. This needs some more thought, but the code for storing them is the same either way.
#jira UE-109586
#rb lauren.barnes
[CL 15802120 by sebastian nordgren in ue5-main branch]
The Favorites category is now always visible, and displays a note about how to add properties there when empty.
#rb chris.gagnon
#jira UETOOL-2769
[CL 15208242 by sebastian nordgren in ue5-main branch]
