celery: change configration behaviour

* Changes celery configuration behaviour to set defaults
  on the application context configuration.
installation: initial Procfile

* Initial version of Procfile that allows easy one command startup
  of the entire stack (web, db, workers, cache, ...), using either
  Ruby foreman or Python honcho.
Merge remote-tracking branch 'lnielsen-cern-github/procfile' into pu