remove acceleration tick from timer3, use the pending sv from stepper tick. this...

remove acceleration tick from timer3, use the pending sv from stepper tick. this keeps it in sync
gets rid of the Timer3 hack to sync it with timer1, and removes a bunch of code.
any module can register with stepticker for an acceleration callback, uses a vector of Lambdas.
right now functionality and period of accleration is the same as it was before.