MIDI profile examples missing call to BeanMidi.enable()

[joebowbeer]

BeanMidi.enable() must be called to add the BLE MIDI service to the bean's advertisements, but neither of the two BeanMidi examples call it:

https://github.com/PunchThrough/bean-arduino-core/blob/master/examples/profiles/MIDI.ino
https://punchthrough.com/bean/docs/guides/features/midi/

The bean's MIDI service needs to be advertised in order for it to appear in the list of available BLE MIDI devices presented to the user by iOS and Android apps.

Suggested fix: Call BeanMidi.enable() in the examples' setup function.