prepare for b2d 0.7.0

- remove unused docker-daemon script
- remove daemon startup customisability - as @crosbymichael notes, users expect b2d to be all magic, and until we have _one_ awesomely working setup, we can't justify the complexity
- add DOCKER_RAMDISK env - https://github.com/crosbymichael/docker/commit/36dd124b16a76704a88142fa96bb4bb6260dd821