[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.

<div id="ajaxroot">
  <h1>Hello</h1>
</div>