Bug 6875 de nesting C4::Biblio

Bug 6875 de nesting C4::Biblio

C4::Biblio is used in many many places. The goal of this cleaning is to do from C4::Biblio a package with as many dependancies as possible.

* C4::Heading is called only in 1 place, highly rarely used (only in 1 misc/link_bibs_to_authorities.pl), moving to require
* PrepareItemrecordDisplay is a sub that is more related to Items, moving it here. It means some scripts that used this sub must be checked against use C4::Items
* C4::Items is needed in EmbedItemsInMarcBiblio, moving it only in this sub, and switching to require
* 2 subs are totally useless z3950_extended_services and set_service_options, removing them

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
No test plan included, but tested some opac and cataloging functions.
Code looks good. Marked as Passed QA.