Finished the random selection of exit survey questions. Added setting DEBUG_SURVEY to always show all survey questions.

Added an exit survey on the profile page. It can be answered once, either directly or through a certificate request.

Certificate request form is now only submitted once. The link shows if a certificate can be downloaded, or is still being generated.

Added UUID generation to certificates. Now, each student/course will have a unique ID for verifying the certificate.

Moved certificate requests to its own application. Fixed up styling on certificate request form. Changed wording of the form.

Added a form on the profile page to request a certificate. Still needs major styling, but the basic back-and-forth works.

Quick heartbeat page that ELB can monitor to detect if gunicorn is up and running or not