WET core: upgraded to jQuery 2.0.0 for modern browsers

If issues are encountered, changes can be rolled back by downloading the
compressed, production jQuery 1.9.1 release from http://jquery.com/download/
and overwritting the WET copy of jQuery which is in /dist/js/jquery.min.js
Merge pull request #2233 from patheard/jquery-2.0

WET core: upgraded to jQuery 2.0.0 for modern browsers