Revision 197784

1.) Combined the AreaTree and FOTreeHandler into a new AreaTreeHandler
object.  FOTreeHandler was primarily acting as an AreaTreeHandler,
and AreaTree had a 1-to-1 relationship with it.  Comments most welcome.

2.) Created convenience methods in FOInputHandler for those subclasses
which do not handle certain signals/events called from the formatting
objects (i.e., AreaTreeHandler).