Bug 11232: MARC21 facet definition and updated XSL file for DOM

This patch adds the facets definitions to the biblio-koha-indexdefs.xml, based
on what is hardcoded on C4::Koha::getFacets().

The biblio-zebra-indexdefs.xsl file for MARC21 is generated using the usual:

xsltproc ...koha-indexdefs-to-zebra.xsl ...marc21/biblios/biblio-koha-indexdefs.xml > \
    ...marc21/biblios/biblio-zebra-indexdefs.xsl
Bug 11232: UNIMARC facet definition and updated XSL file for DOM

This patch adds the facets definitions to the biblio-koha-indexdefs.xml, based
on what is hardcoded on C4::Koha::getFacets().

The biblio-zebra-indexdefs.xsl file for UNIMARC is generated using the usual:

xsltproc ...koha-indexdefs-to-zebra.xsl ...unimarc/biblios/biblio-koha-indexdefs.xml > \
    ...unimarc/biblios/biblio-zebra-indexdefs.xsl
Bug 11232: NORMARC facet definition and updated XSL file for DOM

This patch adds the facets definitions to the biblio-koha-indexdefs.xml, based
on what is hardcoded on C4::Koha::getFacets().

The biblio-zebra-indexdefs.xsl file for NORMARC is generated using the usual:

xsltproc ...koha-indexdefs-to-zebra.xsl ...normarc/biblios/biblio-koha-indexdefs.xml > \
    ...normarc/biblios/biblio-zebra-indexdefs.xsl
Bug 11232: retrieve facets from Zebra's indexes in DOM

This patch adds two routines.
    1) _get_facet_from_result_set:
       Given a result set and a facet index name, retrieve the facets
       for the given index, and build the result for rendering.
    2) _get_facets_from_result_set:
       Given a result set, loop through all defined facets in C4::Koha::getFacets
       and call _get_facet_from_result_set for each, to build the facets
       information.

TODO:
 - mocked unit tests
 - indexes defined for NORMARC and UNIMARC
 - Move all munging code into separate and testable subroutines.