Put more recent version of CrOS SDK for octopus in the octopus.env file.
Docker file changes are required for the new SDK to be build properly.

Signed-off-by: Michal Galka <michal.galka@collabora.com>

Add a Docker container with docker-compose to prepare a Chrome OS
SDK environment to build some Chromebook firmware.  Include a
bootstrap.sh script to set it up and the environment variables
for "octopus" as the first device type.

Signed-off-by: Guillaume Tucker <guillaume.tucker@collabora.com>