Bug 8525: highlight matches on OPAC detail page

Bug 8525: highlight matches on OPAC detail page

After doing a search and going to the details page, it can sometimes
be difficult to see exactly *why* a record was returned by a search.
By highlighting matches on the detail page as well as the results
page, we make it much easier to figure that out.

This patch uses a query_desc CGI parameter which is inserted into links
from the results page with javascript. This serves to avoid the
potential privacy implications of a cookie, and ensures that users
without javascript enabled see no change whatsoever.

To test:
1) Do a search (or two) in the OPAC with OpacHighlightedWords on.
2) View a record or two of the results, and ensure that the correct
   words are highlighted.
3) Disable OpacHighlightedWords and do another search (or two),
   this time ensuring that no words are highlighted.

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>