arduino-mk makefile so I can ditch that craptastic arduino UI
fix some warnings related to passing immediate strings to char* instead of const char*. get rid of strplus.
Move checksum comm function and various debugmessage functions into their own respective .h and .cpp files
Move setting of pid parameters over to new checksum stuff; raise warnings when non-checksummed versions of checksummed commands are received.
Early declaration of stepExtruder function
Move globals into their own .h/.cpp pair. Also rebuild PID control loop to match a real PID control loop.
header inclusion fixups related to new reorganization
Minor fixes to slave initialization banner
Ignore build artifacts from arduino-mk