Bug 11083: Add ability to generate authority summary using XSLT

Bug 11083: Add ability to generate authority summary using XSLT

This patch only affects authority search results in the staff interface.
It adds a new system preference AuthorityXSLTResultsDisplay. If set,
each authority search result MARCXML will be transformed using the XSLT
at the given filename or URL. The output will be displayed in place of
the default summary.
If errors occur, the XSLT is ignored and the default summary is
displayed.

The syspref value can contain {langcode} and {authtypecode} which will
be replaced by the appropriate value (resp. current language and
authority type code)

Test plan:
1. Apply patch and run updatedatabase
2. Verify that authority search results are not affected yet.
3. Create an XSLT file (for instance in
/home/koha/xslt/en/GEOGR_NAME.xsl)
4. Set AuthorityXSLTResultsDisplay syspref value to
/home/koha/xslt/{langcode}/{authtypecode}.xsl
5. Do an authority search that returns GEOGR_NAME results. Verify that
the summary matches what you expect from your XSLT
6. Do an authority search that returns authorities of other types.
Verify that the default summary is displayed.

Example of a minimal XSLT:

<?xml version='1.0' encoding="UTF-8"?>
<xsl:stylesheet version="1.0"
 xmlns:marc="http://www.loc.gov/MARC21/slim"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output omit-xml-declaration="yes"/>
  <xsl:template match="marc:record">
    <xsl:element name="div">
      <xsl:attribute name="class">
        <xsl:text>authority-summary</xsl:text>
      </xsl:attribute>
      <xsl:value-of
        select="marc:datafield[@tag='151']/marc:subfield[@code='a']"/>
    </xsl:element>
  </xsl:template>
</xsl:stylesheet>

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>