An integrity error while creating an enrollment just means that our work has already been done. Fixes https://www.pivotaltracker.com/story/show/46915947

strings.

Added unit tests that verify the fix.

Switch timed_module to store location, and use to navigate from timer when timer displays on non-exam course pages.

If certificate status is 'restricted' the grade
and survey link will be shown, the download link will not

If there is no announcement date (in the policy metadata) then use a
heuristic to sort them.

If there is an announcement date, the use it in the heuristic to
determine if the course is new or not.

Add some log statements. Add missing fields to _make_tc_user, and make _make_tc_registration independent of course configuration (for testing)

The property can be set in the policy metadata. If it is not specified
then it is set to true if the course has not started yet.

Also adds a property to check how many days are left until the course starts.

switch back to returning json to test_center_register template, and enable jquery handling in template.