[#29641] Very slow of JavaScript performance  in Isis... 

As we already know, chosen.js is the cause a low backend performance in some cases.
Patch remove the chosen from all tmpl/ files in backed, and add options to the Isis template for enable/disable Chosen. Enabled by default.
This patch is not a really fix, it the deal between "use" and "not use" chosen.

Links:
* [[#29641] Very slow of JavaScript performance in Isis in Opera](http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=29641)
* [chosen.js is the cause of the low backend performance (in google group)](https://groups.google.com/d/msg/joomla-dev-cms/ShfyM4biFHg/V0f8nJmhOG0J)