Add Transposition function

[catkins]

Fixes #12

• Adds new TRANSPOSE sub-menu to FUNCTION menu on analogue inputs
  • Adds transposition plus or minus 10 octaves and 12 semitones.

[catkins]

I've tested this on a CV thing, but not on a VCMC (as I don't have one), and seems to work as expected.

One small issue I need to figure out that is that occasionally I needed to panic the midi after changing the octave/semitone value. The NoteOff messages may not taking into account the transposition if I've got a sequence running whilst I change the parameter so I'll need to poke around to suss that out.

I'm still finding my way around the codebase, but I assume that will be a fairly easy fix.

[catkins]

Haven't seen the note sticking thing again.

@xustafu @SergioRetamero - are you able to review this PR when you get a moment?

[xustafu]

Sorry for the delayed answer!!! hope to be testing this one on monday. In the meantime, and for organization purposes, do you mind doing the request to be merged to Transpose branch?

[catkins]

Awesome, thanks @xustafu

Updated the base to be the Transpose branch on origin.

Let me know how you go 😁