Add a web and a worker proccess group to supervisord
Switch to different base image for the vagrant vm

The raring ubuntu cloud image has a bug, where the server key for
the openssh-server is not generated on first startup. Somehow cloud-init
is not run like it is supposed to. The image I put in there is
provided by https://github.com/opscode/bento.
Documentation for the Vagrant-dev-setup improved
Fix Vagrant warning about deprecated configuration option