Migrate cell-specific cellPrintValue handlers to a grid-wide
cellTextGenerator handler. This simplifies the client-side API and
helps to formalize the API a bit more by providing a new
GridCellTextGenerator interface.
Warning messages are now display at page load time when a grid cell uses
a cellTemplate but does not have a matching text generator.
Signed-off-by: Bill Erickson <berickxx@gmail.com> Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org> Signed-off-by: Jane Sandberg <sandbej@linnbenton.edu>