Allow output events to target different MIDI buses

[jtackaberry]

Output event should allow specifying bus in addition to MIDI channel. Routing behavior should work the same way as channels, except now targeting across different buses.

The GUI will need to clearly flag conflicts when bus 16 is used and control surface feedback is enabled, since bus 16 is used for feedback.

Bits 8-11 of slot 1 in the output event is reserved for this.

[jtackaberry]

Proposed syntax is [channel][.bus]. As with channel, bus would be indexed from 1.

Has these behaviors:

• If channel is not specified, behavior is as today: it's based on the target channel for the bank's configuration on the track.
• If bus is not specified, again as today it assumes bus 1.
• If bus is specified but not channel, it will route to the specified bus on the default target channel
• Must interop with #42 and #74

Either channel, bus, or both can be specified. Examples:

1. o=cc@12.3:11,127: send CC11/127 to channel 12 bus 3
2. o=cc@.10:11,127: send CC11/127 to bus 10 on the bank's target channel

[jtackaberry]

Connect Vadium on VI-C to validate VEP use-case. Ref.