Chromebook

Added Chromebook support
Updated License
Renamed readme.txt files formatted as markdown to readme.md
Fixed hardcoded uboot source path for Wandboard to a parameter

We try to avoid having people edit the Crochet source files.

I suggest renaming this to CHROMEBOOK_IMAGE_SIZE and:
  * Set it to 0 in board/Chromebook/setup.sh
  * Add a POST_CONFIG check to verify that it's not zero.
  * If it is zero, instruct the user to set it in their config.sh file