BibDocFile: split from WebSubmit
BibDocFile: split from WebSubmit

* Separates BibDocFile source code from WebSubmit source code into
  dedicated module.

* Updates links and admin guide accordingly.

* Moves Document File Manager administrative interface from
  "/submit/managefiles" to "/CFG_SITE_RECORD/managefiles".

* Note: this commit changes most of CFG_WEBSUBMIT_* variables into
  CFG_BIBDOCFILE_* ones, so you may need to amend BibFormat elements
  and WebSubmit functions if you use them in your code.

Co-authored-by: Tibor Simko <c7116e45300b163846dc01f3ed02116e3f8ef7a5@cern.ch>

tiborsimko/invenio-base,inveniosoftware/invenio-base,tiborsimko/invenio-base,inveniosoftware/invenio-base