Added sensors, actuators, PWM code

Added sensors (analog + digital), actuator (digital) and some PWM code - kept in separate files currently, but it should be evident what goes where. Need to write separate functions to make code neater with filepaths etc. Added .rar file containing useful examples of BeagleBone IO coding.

Also deleted my old sensors folder since most of it was irrelevant (moved some stuff to the BBB code folder).