Bug 19436: Add SRU support for authorities

Bug 19436: Add SRU support for authorities

Test plan:
 - Apply the patch
 - Add an SRU authority server in admininistration -> Z39.50/SRU servers
   You can try with the French national library, configured as such:
   Hostname: catalogue.bnf.fr
   Port: 80
   Database: api/SRU
   Syntax: Unimarc
   Record type: authority
   Additional SRU options: version=1.2,sru=get
   SRU Search fields mapping example:
	Keyword (any): aut.anywhere
	Name (any): aut.anywhere
	Author (any): (aut.type any "pep org") and aut.accesspoint
	Author (personal): aut.type=pep and aut.accesspoint
	Author (corporate): aut.type=org and aut.accesspoint
	Author (meeting/conference): aut.type=org and aut.accesspoint
	Subject heading: (aut.type any "geo ram_nc ram_ge ram_pe ram_co") and aut.accesspoint
	Subject sub-division: aut.type=ram_pe and aut.accesspoint
	Title (any): (aut.type any "tic tut tum ram_tp ram_tu") and aut.accesspoint
	Title (uniform):(aut.type any "tut tum ram_tu") and aut.accesspoint

 - Try a search from Authorities -> New from Z39.50/SRU
 - Check that the authority is correctly displayed in "Show Marc"
 - Check that the authority is correclty added to koha in "Import"
 - prove t/db_dependent/Breeding.t

Signed-off-by: François Pichenot <fpichenot@ville-roubaix.fr>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>