Add ViewBinder & setText APIs to match SimpleCursorAdapter

There's nothing new here, just a clone of the ViewBinder API from
SimpleCursorAdapter.  This provides a much more lightweight way to
override data mapping on an item-by-item basis.

Possibly to-do, but I would rather leave for another CL:
(1) Better handling of expanded/contracted group & last child (footer).
(2) Cached info map (see SimpleCursorAdapter) for performance