add new incubation example using bitcrusher FX - need to test on RP
Fix wobble FX using pulse control wave form:

unlike lf-saw, lf-tri and sin-osc, lf-pulse emits signals between 0 and 1
rather than -1 to 1. Scale appropriately to match other control waves.
Teach slicer to use different waveforms for modulating amplitude.
enforce ugen rate to be specified in selects.
minor synth doc additions