Bug 29418: Make clean_search_term escape double quotes

Bug 29418: Make clean_search_term escape double quotes

We noticed that several characters will break Zebra queries. So search
terms need to be quoted for things to work. In this context, double
quotes inside search terms are problematic because double quotes are
what we use for quoting strings.

This patch makes the clean_search_term method escape double quotes.

To test:
1. Apply the unit tests patch
2. Run:
   $ kshell
  k$ prove t/Koha/SearchEngine/Zebra/QueryBuilder.t
=> FAIL: It doesn't work as it should!
3. Apply this patch
4. Repeat 2
=> SUCCESS: It does the job!
5. Sign off :-D

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>