WidgetFunctions now extends dire.ValidationInstances

Useful if you need VSIn's applicative functor
Cleaned up efa.nb.controller.Saver

Added class `SavableInfo` to conveniently wrap up all info
needed to create a `Saver`.
Fixed StateTransFunctions

Adjusted efa.nb.controller.StateTransFunctions to compile against
the latest version of dire.swing.undo.