Initial attempt to switch to the new interactive widgets
 Changing the way `display' handles the interactive widgets

- All the inputs to the function are laid out and available for input
  in a single form instead of having a wizard-like dialog.
  Consequently, got rid of the continuations business.
- Generic instances fixed, instances for sum types should work
  correctly now
- (Maybe a) values are inputted using a checkbox

Thanks to Luite & Brent for writing down the core code for this.