Extend support in flock.midi.controller to all appropriate MIDI message types

[colinbdclark]

Currently, the flock.midi.controller component provides a (still somewhat awkward) means for declaratively mapping incoming MIDI control and note on/off messages. However, it doesn't support other types of messages such as pitchbend, aftertouch, etc.

This should be remedied by restructuring the component's options to have a "mappings" object at top level that can contain keys for each MIDI message type (i.e. control, noteOn, etc.).