#51: A little more work on rich documents
#51: A little more work on the rich document model.
#51: Implemented more of RichDocumentModel.  Really just missing some
listener code now.
#51: Added style listeners to the MuisDocumentModel interface.
Implemented style listening in SimpleDocumentModel and
WrappingDocumentModel.
Began converting some selection listeners to be style listeners where
appropriate.

Need to finish that conversion and implement style listening for
RichDocumentModel.
#51: Finished integration of the style changes and added code I forgot
to fire style changes from the simple model when the underlying styles
change.
#51: Fixed build errors and added stubs for new listeners in the rich
model.