Backported dataAvailable to 2.4
Merge pull request #1112 from djbobke/2.4-dataavailable-squash

Backported dataAvailable to 2.4 from 3.0
Add CakeRequest::param()

This method gives a read accessor to the data in $request->params.
It removes the need to use isset() and empty().
Merge pull request #1116 from markstory/request-param

Add CakeRequest::param()
Added JSONP support for JsonView
Changed params for HtmlHelper::css() to be consistent with HtmlHelper::script().
Closes #3593