[racket-dev] "Add Teachpack" dialog can be very confusing

Opening up the "Add Teachpack" dialog presents the user with two lists
of libraries, which overlap in exactly one case: "image.ss". This
makes it very easy for the user to choose the old image.ss library
when working with HtDP2e. Further, there's no indication in DrRacket
as to which one of these was chosen.

I can think of a couple ways this could be improved: the HtDP2e
prologue could be explicit about which pane of the dialog to look in,
and the dialog itself could ask the user which book they're using.
Also, it would be great if DrRacket said "Teachpack: image.ss (from
HtDP)" in the language position. Or we could just hide the old
teachpack.

Sam

PS: the Add Teachpack dialog has no title on my machine, or rather
it's just titled "DrRacket".