major cleanup

Removed commented-out code, deleted old testing files, fixed some commenting

This builds but has not been tested!
started added conditional compilation flags

also added method for checking the proper chip is selected

deleted code for the MX4ck board (pic32mx460), as we aren't using that anymore
added rest of compiler option framework and guard code
tweaked main file for conditional compilation across different boards
renamed timer 1 to sensor timer, generalized timer configuration
fixed SPI ISR bug

the idle flag was never getting set to "false" (it was always true)
Added framework for the thruster LED board
Added framework for the thruster LED board
Major system architecture change. Framework should be ready for code porting
Thruster LED board framework is done.  Just need to fill in the LED pin mappings
sensor board porting framework mostly complete
More porting support for the other boards
framework for signed byte motor commands complete
removed computer-side python interface files
added GPIO framework
More porting
PPS is set up
changed compile flag
added support for the magnometer
removed unnecessary UART loads in the sensor timer ISR