Support multichannel instruments

[rualark]

General approaches:

• If each channel can have different names of same cc/ksw, then each channel should have separate cc/ksw mapping. Difficult to implement.
• If all channels have same names of cc/ksw, but they can have different values, then initialization should be different for each channel. Difficult to implement. In this case different parameters of different channels should have different cc/ksw numbers.
• If all channels have same сс/ksw values, they can be copied to all channels. In this case different parameters of different channels should have different cc/ksw numbers.

[rualark]

Sending dynamics cc in LASS:

• Dynamics CC should be sent to legato, tremolo, harmonics and (possible) trills, sordino
• Vibrato CC should be sent only to legato patch
• Other CC are sent only with note starts (cc83)

The problem with dynamics cc is that as music moves from one articulation to another, cc should follow. Approaches:

• Send dynamics CC to all 5 channels simultaneously. This increases size of midi files, reaper load times, php midi load times. Most simple solution.
• Send dynamics CC only to channels, which are used at least once in track. This is a simple solution and will reduce MIDI file in 95% of situations.
• Send dynamics CC to all 5 channels simultaneously, but then delete dynamics if there are no notes in this channel within 1 seconds range. Not a simple implementation, but generates convenient MIDI
• Switch to a different channel for each note. This is a very problematic solution, because it requires to find points of switching between channels.

[rualark]

So, the most simple solution is just to duplicate all cc and ksw in all channels of an instrument. Removing unneeded ccs can be done this way:

1. Scan through all notes until first note of needed channel is found. Remove all dynamics CCs before this note.
2. Go to next note in this channel. Check if it is separated with distance longer than 2 seconds. Remove dynamics CCs in between.
3. After approaching last note in this channel, remove all dynamics CCs after it.

[rualark]

Todo:

• [x] Add "channels" parameter to instrument config (number of channels used).
• [x] Add "channels_dyn" parameter to instrument config (number of channels using dynamics)
• [x] Add "channel" parameter to instrument config (for fixed channel instruments)
• [x] Add "pizz_chan", "stac_chan", "trem_chan" parameters to instrument config