Selecting an element should make that row active.
Fix fps display.
Combine parallel intents on discrete elements by color in a highest value wins.
Reset element states in a common place so all sequence end events reset the states. Solves a bug where autoplay of a small section left the element states hung.
Fix the threading issues with the background renderer.  It was blocking waiting for more elements, so was never gracefully finishing. We do a few things now:

1) CompleteAdding() to the blocking queue, so it stops blocking in the background worker,
2) give feedback to the main thread that it is completed (with a ManualResetEvent), so it can wait for it to finish.  (This would be what the RunWorkerCompleted event would be for, which is run on the main thread.  However, that requires the message pump to be run to process the event, and it's bad JuJu to use Application.DoEvents(). )
3) we don't expect any particular exceptions in the background worker.
Merge remote-tracking branch 'remotes/jeffu231/master'