bug 2692: remove escape="url" from opac-facets.inc

bug 2692: remove escape="url" from opac-facets.inc

Based on Owen Leonard's patch, but redone to exclude
a dependency on an earlier unapplied patch.

For future enhancement, limit_cgi and the like should
probably not be constructed directly in C4::Search.
Instead, it should pass back a representation of the search
that the template can use to construct the appropriate URLs.
Done right, that would also make it easier to implement
things like search history.

Signed-off-by: Galen Charlton <galen.charlton@liblime.com>