Rewind should reposition score

Periodically, someone on forums requests that the Rewind button on the toobar should actually reposition the canvas immediately rather than waiting for playback. In the past, a case might have been made that there was value in decoupling these actions - that rewinding the playback cursor shouldn't necessarily reposition the canvas. Now that the "Pan score automatically" button is honored for all actions, though, I propose that be the decoupling mechanism. So, rewind repositions the canvas to the begining of score if "Pan score automatically" is enabled (the default), but doesn't if it is disabled. A simple change, PR forthcoming.