legacy: oaiharvest admin import fix

* Improves PEP8 and PEP257.

* Temporary fixes wrong imports. (addresses #2188)

Co-authored-by: Esteban J. G. Gabancho <esteban.gabancho@gmail.com>
Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
websearch: circular import removal

Signed-off-by: Esteban J. G. Gabancho <esteban.gabancho@gmail.com>
indexer: legacy admin interface fixes

* Fixes the admin interface of bibindex. (closes #2190)

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

* Adds all the admin interfaces to the `/admin` page.

Co-authored-by: Jiri Kuncar <jiri.kuncar@cern.ch>
Signed-off-by: Esteban J. G. Gabancho <esteban.gabancho@gmail.com>