[#33838] Generate version of atom feed from JVersion

http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=33838&start=0

## Testing Instructions
Check an atom feed of a component (e.g. article category view). Before patch the < generator > tag will show the version as 1.6. After patch it will show 3.3 (and pulls the version number from JVersion so will not need updating in the future)