Refactor geoweb to use Daemonizer and DropPrivileges plugins

Allow geoweb to drop privilege when run as root.
Make the ESGF download directory configurable

Rather than downloading files to a temp directory
use DATA_ROOT to configure the location.
Merge remote-tracking branch 'origin/111-staticdir-download'

* origin/111-staticdir-download:
  Make the ESGF download directory configurable
Merge remote-tracking branch 'origin/126-drop-privilege'

* origin/126-drop-privilege:
  Refactor geoweb to use Daemonizer and DropPrivileges plugins