Steps toward a usable UI --- in particular, document PropertyBinder.
Steps toward a usable UI --- in particular, document PropertyBinder.

Also, eliminate the initial feints towards PreferenceScreen handling;
there are better ways, and they'll be coming up.  (I may also fold at
least the public PropertyBinder API into UiBinder, just to make it a
one-stop shop as far as clients are concerned.)

rst/positronic_net