TapeUI doesn't clear when machine resets

[mikejsavage]

.

[rgossiaux]

I think the cleanest fix would be to add a reset event that StackMachine would pass to listeners. At the moment when it resets it fires a lot of StoreChanged messages, and distinguishing these from normal stack usage could get real ugly real fast.

I'm about to play croquet but if this is still open when I get back I might deal with it that way.