Specific example of undo that is working is using the autocomplete search to add a new node and its neighbours
Last few commits attempted to start the interaction model with a menu (calls of it, calls by it) to try a more complicated undo scenario (for purpose of trying to revert the entire graph display model rather than the action based approach used for undo search action). However, that's turning out to be more complicated and this branch's scope is growing too much. So will continue this work on #12
Fixes #14