Wip webapp paths

I've fixed the problem with saving interactives. This was just one symptom of a number of problems after moving the file based interactives to the top-level dir. 

This branch is deployed on lab3.dev.concord.org. The webapp, non-file, based interactives are located at lab3.dev.concord.org/webapp. (*note* would like to change this 'webapp' path to be configurable and to replace where I've hardcoded this "webapp" string in code.)

Had to change the rails routes, import code, Makefile to create a symlink in server/public but most of the changes where in the application.js.

No PT story for this but I'll update the Datagames PT bug at https://www.pivotaltracker.com/s/projects/731349/stories/49005035