First commit of EV3 Sensor Library

Arduino library for EV3 UART sensors using SoftwareSerial. I am one of the leJOS developers.

This library deals with all EV3 UART sensors and modes but has not had much testing. It would be useful to have a discussion about the API.

I also have leJOS running on the BrickPi but think we will need custom firmware for  it to work well, so I am going to start looking at that, including incorporating EV3 UART sensor support.