Remove jQuery, replacing the default Ajax by a minimalist implementation

I removed jQuery and adapted the jsRouter that was (AFAIK) the only dependency on jQuery.

* Use http://jsbeautifier.org/ to review the Javascript code
* Since passing "None" to ajaxMethod no longer makes sense (we always have an Ajax function), I made it a String instead of Option[String]
* Including jQuery is enough to use it for the Ajax calls, and you can still pass a different method