Add redex enum support for simple named repeats
Remove unnecessary names before enumerating.
Follow 480afa4c4de10ff428521405b6b9718a1edba055 in deinprogramm.

Abstract out the teachpacks dialog and re-use in DMdA languages.
Add (very simple) type for `hash`.
fix the conversion to a [0,360) interval for angles in 2htdp/image

closes PR 14071
Fix TR constructor detection.

Was accidentally turning #%expression into #%plain-app in some cases.
fix image list coercion

unbreaks place-image in the case that it gets bitmaps directly

Also, bring test-image.rkt down below 102 columns
test for stop-when problem with booleans
fixed test with display line
Added `point-label3d', notion of layers (back, area, front) to 3D plots
Add chapter on concurrency to the Guide