Center switch for LFOs

[attilammagyar]

Currently LFOs oscillate between min and min + amount * (max - min), which makes it cumbersome to use them for vibrato by assigning them to the Fine Detune parameter of an oscillator, especially if one wants to also control the amount of the modulation.

This could be simplified a lot by adding a toggle switch to each LFO which would make it oscillate between (min+max)/2 - (max-min)*amount/2 and (min+max)/2 + (max-min)*amount/2.