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>