Initial commit with minimal set of files to build an image.

BUG=chrome-os-partner:28940
TEST=./setup_board, ./build_packages, ./build_image

Change-Id: I5644889df9b3555ddc92833d86d49e3ad23aa896
Reviewed-on: https://chromium-review.googlesource.com/198320


Reviewed-by: Katie Roberts-Hoffman <katierh@chromium.org>
Commit-Queue: Shunqian Zheng <zhengsq@rock-chips.com>
Tested-by: Shunqian Zheng <zhengsq@rock-chips.com>