[#33585] [imp] JTable improvement to the bind method

http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=33585&start=0

In many of our JTable classes (see examples for contact and newsfeeds) we repeat the same code over and over json encoding some fieldsets with JRegistry. In this PR I abstract this out into the parent JTable::bind() method to make it more DRY - now all you have to do is create an class array with the array of data you wish to json encode.

I've applied this to the contact and newfeeds components and it's allowed me to remove the entire bind overridden function in exchange for just this class variable

It's 100% b/c with any existing code as the class var is left empty in the parent JTable method.