Claytone/adding shortcuts (fixed conflicts) + added highlight scope

[coderofsalvation]

(milkytracker editmode) liveperformance keys used: ctrl+ [shift] + [ m / left / right]

This basically is https://github.com/milkytracker/MilkyTracker/pull/281 but:

• mergeconflict has been solved
• ctrl+m now also toggles mute of current channel
• the current channel is highlighted in the scopes (to make muting/editing more obious)

it's a breeze to use on a laptopkeyboard during liveperformance, especially in combination with https://github.com/milkytracker/MilkyTracker/pull/291 and https://github.com/milkytracker/MilkyTracker/pull/288

[coderofsalvation]

thx! already merged in v1.04