UART sensors

EDIT: This has been superseded by #19.

I think I have UART sensors working pretty decently now. I simplified them per your suggestion and got rid of the device classes. All attributes are on a single device node on the legoev3 bus now. I will be posting a HOWTO wiki page shortly on how to actually use it.

I have packaged the kernel and modules so that you don't have to compile them in order to try it out. For everything to work, you will need to install the ```ev3dev-uart``` package from the ev3dev ppa as well.

As root:
```bash
wget -P /etc/apt/sources.list.d http://ppa.lechnology.com/ev3dev.list 
apt-key adv --keyserver keyserver.ubuntu.com --recv-key 1F8AF88C82F77C03
apt-get update
apt-get install ev3dev-base linux-image-3.3.0-ev3dev-00.01.02-dlech-g4fb6ed4
cp /boot/uImage-3.3.0-ev3dev-00.01.02-dlech-g4fb6ed4 /media/mmc_p1/uImage 
reboot
```