Performance - HTML decode uses DOM directly rather than jQuery to speed things up

- Based on the discussion in forum thread 16961 and the results from
  http://jsperf.com/html-decode I've updated how the HTML decode for
  filtering is done to bypass jQuery and use DOM methods directly. It is
  more code but it is also much faster.
Performance: On destroy, don't select tbody elements for event removal

- Based on thread 17024 - if you have a large table with a lot of
  elements in the tbody, the find('*') selector was of course selecting
  them all. That results in poor performance. DataTables doesn't add any
  events to the children in the tbody, so we can filter out those
  elemetns and keep the element list ot  a sensible size.