Bug 25639: Add search query strings as global javascript variables

Bug 25639: Add search query strings as global javascript variables

To test:
1 - Search on OPAC for "qwertyuiop"
2 - View the HTML source
3 - Find 'qwertyuiop' in the source, it is not easily accessible via JS
4 - Apply patch
5 - Repeat
6 - Note that now there are global variables with the query strings
7 - Add to OpacUserJs:
    console.log( query_desc );
    console.log( querystring );
    console.log( query_cgi );
8 - Reload page and confirm variables are warned in the JS console (Press F12)
9 - Sign off

Signed-off-by: Sally <sally.healey@cheshiresharedservices.gov.uk>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>