A framework around the USART communications...

Three types of messages:

  - a value update from the PC.  Value name is a letter from A-Z, value value is 00-FF.  Format is something like "\e#sAFA" (Send) to update pin A's value to FA.

  - a value update from the PIC.  Value name and value is same as above.  Format is something like "\e#uAFA" (Update) to update pin A's value to FA

  - logs sent from PIC.  Message is arbitrary, but must not include "\e#"

Valid pins include:
	A-Z		byte "pins".  Values can be 00 - FF
	a-z		bit pins.  Values are 0 or 1