Revert "[mr3035] fix broken "manual" invite after 3023, thx to mns."

This reverts commit 948c7bf915aee07988c4f7c82907b3217ca89738.
[mr3036] try prevent group looting without group (cheat?). related to #1415.
[mr3037] Always cleanup GroupGuid/OriginalGroupGuid while set new group or remove from old group. remove static RemoveFromGroup() method - source of problems. possible fix bug-using problems, identified after 3023, also some speedup. testing.