Cleanup. Removal of unused/dead code.
Moved some calculations from lookahead to execution phase. And thus reduced the numer of items in the move5D data structure.
Started implementation of move optimization: Add routine to traject.c that can implement the best speed vector change based on the current and next move.
Added compiletime option to disable the comm task by defining NO_COMM_LAYER. This  prevents serial i/o processing  and keep-alive message generation.
Implement fan PWM with M106/M107

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
Implemented full control of all PWM devices (extruder, fan and bed), backwards compatible with simple M7/M9/M106/M107. Increased default PWM frequency for extruder and fan for less noise.
Fix floating point error when no analog channels are defined.
Implemented a dummy channel that has always the right temperature.
add config for Beaglebone + Makergear M2

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
M2: change bed thermistor

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
m2: fix axis length, e-steps and up PWM freq

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
m2: checkpoint

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>