Minor refactor of NewWindowWidget().
Fixed an embarrassing bug in ContainsWidget().

This is why "declared and not used" errors are quite good. I'm not sure
why this didn't trigger it.
Modernized TextFieldWidget to use font size and correct coordinate system.
Add Layout() that propogates via Widget.Layout() to TextFieldWidget.
Added Delete key support to TextFieldWidget.
Add SearchableListWidget and change Test5BWidget to use it.

Add support for multiple keyboard selection to ListWidget and
TextFieldWidget.