Notify plugins of all commands being executed

For some kinds of plugins, knowing which commands are being invoked by the user are critical.

E.g., a panel plugin can watch the scenegraph changes (though not entirely reliably), but would have to “guess” what certain changes “mean”. E.g., is a newly-created object the result of pasting or creating anew?

If a plugin could be fed all the commands the user is invoking (whether by menu or keyboard), it could much more reliably and usefully track changes to the scenegraph.

This won’t be a feature like this in the near term, but we will put this in our backlog