fixtures: port to extension with signals usage

* NOTE `inveniomanage demosite create` is obsolete. All actions are
  executed during `{post,pre}_command` signal handlers.

Co-authored-by: Esteban J. G. Gabancho <esteban.gabancho@cern.ch>
Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
access: removal of site specific configuration

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
search: ids removal from format fixtures

Signed-off-by: Esteban J. G. Gabancho <esteban.gabancho@gmail.com>