(because rails requires these files/directories all the time)

- rename DOCKER_USER as DOCKERUSER (docker-compose seems to fail with
  varnames containing underscores)
- remove quotes

prepare.sh now needs to be sourced only once (when bootstrapping
the containers)

-> enforce authorized_keys format with no options

- display all waiting apps (not just the first one)
- remove the sandobox panel (keep it only on webapps_path)
- remove dead code
- redirect webapps#destroy to myapps