supervisord conf for celeryd; added to install.sh,update.sh
mv entity_add_file to webui.tasks; plug into webui.views

- For some reason the add_file() function did not work if it was
  located inside ddrlocal.models.file or ddrlocal.tasks.
  It only worked when moved inside webui.tasks.
error checking on entity instantiation
add ddrlocal to INSTALLED_APPS