Add JHtml Tabs deprecation

Add in deprecation of subpackage and JLog to mark as deprecated. See google groups discussion here:

https://groups.google.com/forum/?fromgroups=#!topic/joomla-dev-cms/H6IRbyvnP1I

'Feature' request here: http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=30456

Would be nice to get this into 3.1 so people have as much time as possible to get moved across!