Add a trivial image building implementation

to run this:
$ sudo usermod -a -G docker $USERNAME
$ ./contrib/lp-cedarish/docker/prepare
$ solum-builder-api &
$ curl -X POST -H "Content-Type: application/json" \
    -d '{"name":"nodejs", "source_url": "git://github.com/paulczar/example-nodejs-express.git"}' \
    http://127.0.0.1:9778/v1/images

part of blueprint lang-pack
Change-Id: I0105c2ff8787f509c87708b3af863ca2042aa444
Merge "Add a trivial image building implementation"