[web/data] Remove broken jquery-json plugin (closes #3590335) Conversion of Date() objects is somehow broken (don't know why beyond that it's due to jquery-json's monkeypatched Date.toJSON() method). Use the now-standard JSON.stringify() instead. http://caniuse.com/#feat=json says it's supported by all browsers, and even IE going back to version 8.

cubicweb-web: embedded-javascript-library usr/share/cubicweb/cubes/shared/data/jquery.js