Undo (and Redo) for Noctua

[hdietze]

Minerva provides undo and redo for models.

[kltm]

This includes meta-calls to see what the current undo/redo stack looks like.

This should be relatively easy to implement as they are success/failure rebuilds.

However, this should not be attempted until #16 is solved--I don't want to imagine the chaos of getting these things out of sync.

[kltm]

Talked to Heiko, this is all ready to go at the Minerva end.

[kltm]

Now that #16 is technically cleared for now, need to ensure that the layout update query is run on all redraws and merges.