Preliminary use of config.metabib_field values in misc_util.tt2

Preliminary use of config.metabib_field values in misc_util.tt2

Currently, in misc_util.tt2 various record details like isbn,
title, author, etc are loaded by using hard coded XPath expressoins.
Similar XPath expressions already exist in config.metabib_field.xpath.
This code demonstrates that the database variables can be used in place
of the hard coded XPath expressions.  Thanks to Dan Scott for providing
me with the regex needed to make the database XPath values work
within TPAC.  As the code stands now, it loads an array of values
from config.metabib_field into the ctx variable.  This gets done in
the fetch_metabib_field_xpath_and_label function within
OpenILS/WWW/EGCatLoader/Util.pm file.  This function is called in both
EGCatLoader/Record.pm and EGCatLoader/Search.pm.  In the file
misc_util.tt2 the values loaded in Util.pm are looped over until
the entry for ISBN is found.  Then, the XPath value for ISBN is
used after applying the previously mentioned regex, so the TPAC
code can grab the various ISBNs for a record.
Signed-off-by: Liam Whalen <liam@liamwhalen.com>