Add Raspberry Pi with PiTFT support script

This creates an image for the Raspberry Pi with PiTFT from Adafruit support.
Unfortunately, the changes required can't easily be added to the normal script
so we have to use a custom image for the PiTFT.

This also makes the PiTFT be the default console.
Merge pull request #25 from steev/master

Add Raspberry Pi with PiTFT support script