access: site specific configuration of demo roles
access: site specific configuration of demo roles

* Adds simple hack for overwriting demo roles and authorization using
  the site configuration instead of hard coded values.

Signed-off-by: Lars Holm Nielsen <7eaffca9f7cd98839b5821d0d23e09ff764b82cd@cern.ch>
Reviewed-by: Jiri Kuncar <2bdffcb416fed3002465740d19a053a39918cbe5@cern.ch>

tiborsimko/invenio-access,tiborsimko/invenio-access,inveniosoftware/invenio-access,inveniosoftware/invenio-access