Rest entry in real-time (automatic) note input mode

One thing that strikes me as a usability weakness in the new real-time (automatic) note input mode is that everything basically stops when you lift a key (and resumes when you press down a new one). This makes it awkward to use for any musical line that includes rests—a little bit awkward if there is one rest, and increasingly very awkward the more often rests occur.

Suggested change of behavior: the cursor should continue advancing until the user stops it (with Esc), so a rest can be entered by simply not playing on a beat.