Open a top-level window.
Add basic stimuli data entry screen.

I'm not 100% happy with this layout.  It doesn't line-up right vertically, and
the placement of the Add and Delete buttons are kind of awkward.  I'll need to
think of a better layout.  Additionally, I need to think of how to support
undo/redo as well.  Command pattern and/or prevalence to the rescue.