Add convenient getter to fader model
Rename model attributes, add values object
Add step and value code to pot model
Rename variables to match earlier commit
Add debug log to FaderView
Remove dependency on dual osc controls

Now uses arrays to specify as many or few osc controls and
associated vcas/vcos as desired.
Add padding as data on fader model

... to use in collision detection of fader 'switch'
Rename type pot and add convenience methods