rewrite AddGroupsAction

to get rid of GroupSet
adapt groups.jspf to the rewritten AddGroupsAction
adapt ListRemoveGroupsAction to the rewritten groups.jspf
remove WebSessionSet as it isn't referenced any more
remove WebRhnSet as it isn't referenced any more
remove SelectableWebList as it isn't referenced any more
remove WebList as it isn't referenced any more
Automatic commit of package [spacewalk-java] release [2.3.97-1].