Hide points in "formal mode without movement"

Summary:
Displaying the points on polygons that don't visibly move made
the transformer look less like a static image, and more like it
*should* move. This creates a visual distinction between when
the shape will move, and when it won't (except for lines :( )

Screenshots incoming.

Test Plan:
 * switch between formal without movement and other modes
 * make sure the points are hidden in formal without movement mode
 * switch the shape to "2 lines" and make sure that the double
   removal of points (one for formal mode, one for being a line)
   does not cause any js errors
 * try solving a problem in "formal without movement" mode, and
   make sure it still grades correctly

Reviewers: alex

Reviewed By: alex

CC: eater, khirasaki, alpert

Differential Revision: http://phabricator.khanacademy.org/D5882