use MIDI macros instead of hex
built-in plugin description & port-documentation
add channel-filter to 'enforce scale' plugin & document it
fix and document key-map filter

remember note-on/off count, don't send multipme note-on/off messages
if different input notes are mapped to the same output note.
also keep track of these beyond config-changes.
NOOP - variable rename
some more end-user documentation