make --controllerDebug filter for the signals that already accounted for

The --controllerDebug flag is very helpful in exploring what signals are sent back and forth between the machine and the controller. As soon as enough signals are implemented -- especially the output level --, the output becomes so verbose that it's useless. Upon pressing a button, it's virtually impossible to find which signal belongs to it.

I'd hence suggest to add another flag that shows midi flags, but filtered. One useful thing would be to filter out output signals, for example.