AJAX debug

When opening an AJAX endpoint URL in a new tab, Drupal returns the AJAX response in a textarea tag.
This is to maintain compatibility with some old browsers: #1009382: Several popular browser extensions corrupt AJAX responses, causing errors

However, it means that the JSON structure can not be easily inspected in the Firefox JSON inspector.
So this module removes the textarea tag and returns a plain JSON response.

#3568495: Remove IE support from AjaxResponseSubscriber will remove the textarea tag and make this module obsolete.

This module should not be enabled in a production environment.