Callback functions for single wire data reception
Made global vars unique
Callback functions for uart data reception
Singlewire: sanity check for callback function
eeprom_io: simplified load function
First draft of new message system
Major changes

Added null ptr check to callback dispatch, made defines unique, replaced
for loops by memset, removed bogus 'extern' stmts and refined callback
  functions
Keep \n at end of message
Master: Simplified communication relay