Working towards full DMA integration

DMA for output event scheduling is here, but currently uses about 2x the CPU as the original, non-DMA version, and actually produces more jitter. It is disabled by default.  
Other notable changes include:
* the default scheduler no longer compensates when it falls behind (for simplicity; feature may be brought back at a later date)
* Slight changes to homing routine code
* Different default pins for KosselPi