WIP Merge branch 'master' into next

    * master: (29 commits)
      BatchUplader: fix for permission checking
      inveniogc: guest users gc optimization
      inveniogc: clean up gc tasks
      BibSched: authorization typo fix in BibTasklet
      BibCatalog: ticket_submit() docstring update
      WebSearch: CERN-specific video latest additions
      WebSearch: CERN-specific lecture latest additions
      WebSearch: improve detection of record owners
      WebSearch: better retrieval of record tabs
      WebSearch: fix IndexError in is_hosted_collection
      WebSubmit: fix access restrictions in /uploadfile
      WebSubmit: allow record owners to upload files
      BibDocFile: escape file URLs in /files tab
      BibDocFile: fix type of bibrec-bibdoc connection
      BibDocFile: get_icon() for smallest size icon
      WebSubmit: allow image conversion of .tiff
      WebSubmit: grant access to the superadmin as owner
      BibFormat: add sponsor information to copyright
      WebSearch: CERN-specific hack for latest additions
      installation: lxml recommended
      ...
    
    Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
    
    Conflicts:
        INSTALL
        invenio/legacy/websession/inveniogc.py
        invenio/legacy/websubmit/functions/User_is_Record_Owner_or_Curator.py
        invenio/legacy/websubmit/webinterface.py
        invenio/modules/formatter/format_elements/bfe_copyright.py
        invenio/modules/knowledge/api.py