Now in fteapot you can select any one of the buttons in a modal dialog
with the cursor keys and hit enter and it will be selected.
Fixes#17.
In addition, I clarified that the block attribute options will either set
every cell to bold (say), or unset every cell, or you can cancel to not
actually go through with the block operation.
These changes required adding a custom FLTK dialog, tpt_choose.{h,cxx}.
Along the way, I reflowed fteapot.fl to make it more readable for further
coding.
Finally, there is a small amount of additional prep for color support
that (unfortunately) got mixed in with these changes.
Glen Whitney