Revision 196787

1. convert fo.FOTreeHandler to fire events when it completes a PageSequence or document object
2. move logic that starts layout from fo.FOTreeHandler to apps.Driver.
3. add logic to apps.Driver to handle the events fired from fo.FOTreeHandler
4. end result is that FOTreeHandler now allows other objects to handle page-sequence and document objects in a manner similar to the way SAX allows them to handle XML elements.