Need an Undo button

[KnowledgeGarden]

There is the need to "undo" a game move, that is, some node added to a game tree, if the guild changes its mind.
Undo -- or any form of delete is complex but reasonable.
If, however, a node is not a leaf node, that is, it has not only a parent, but also one or more child nodes, then we have to draw the line and declare a rule which says it cannot be deleted. If, OTOH, the guild starts deleting all the child nodes, then that node is now free of constraints which precluded undoing or deleting on it.
TQTopicMap is being modified to support both Undo and full Delete.