ShapeSheet comments

[gwideman]

In the interests of allowing sane development practice to be applied to ShapeSheets, how about the ability to attach comments to the ShapeSheet.  This could be something like an additional Comment cell on each row (or DevComment cell, to avoid conflict). Or it could work like Excel cell comments, with some way to reveal them all.

This idea would also work very nicely with my other suggestion for a plain-text format for exporting (and editing) ShapeSheets, and turn such text into more-usable documentation.