Allow setting a pathname for docker executable

docker executable ships as `docker.io' on Debian.

Usage:
$ DOCKER=docker.io ./build.sh
Check that Docker executable is ok
Fixed bash syntax
Used boot2docker vagrant image
Do not divert initctl with dpkg
added rtail tool to multiplex log
do not use /tmp for supervisord socket
more pep8
Clean
Revert Vagrantfile with ubuntu precise image
Build base image with kameleon
Added node-colmet image unsing its own kernel (qemu)
Gathered some image packages
Fixed oar-node script
Install colmet on the server
Deployed colmet node
Merge branch 'master' of github.com:oar-team/docker-oarcluster

Conflicts:
	build.sh