Fix: Nested DataTables could have their events interfear with the parent tables

* DataTables uses custom jQuery events which propagate up through the
  DOM, with the custom event being triggered on the table node. Ideally
  I'd like to change the event handling to use $().triggerHandler() to
  avoid this issue, but as discussed in issue #245 that would mean that
  delegated events wouldn't work. Perhaps there should be two forms of
  events triggered by DataTables, those which do bubble and those which
  do not. `init` is the only one which would _have_ to bubble.
* The workaround for the moment is to check that the settings object in
  context of the executed settings handler is the same as the one that
  was used in the addition of the event handler.
* This fixes DataTables/DataTables #361