[#33779] JLayout and Event cleanup of categories views

http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=33779&start=0

This gets the categories_default_items JLayout to actually output data

It also adds in a more standardized set of events and implements this into the JViewCategories class
I'd suggest you to use an array for data. Yes, objects are used everywhere but most renderers out there use an array of data so the more standard we are the bettter.