Efficiency improvements with a space

[fijam]

A minor improvement is possible when entering a space - see if we can just press Vol+ without messing the logic up.

Vol+ (9900) was not originally calibrated for, but we can extrapolate it from Stop (7100) and Track Mark (11900)

(wiper stop + wiper track mark)/2 + 1 would give a good approximation.

This should save a couple button presses but may not be worth the added complexity.

[fijam]

Preliminary work done by adding calibration: VolUp to settings.conf

rev2a boards have the value for Vol+ stored in eeprom

[fijam]

rev3b boards also have the Vol+ value stored in eeprom