Add mitxmako.middleware to fix workers

If mitxmako.middleware has ever been imported, then render_to_string
works correctly (which is why we didn't see this in the rest of
edx-platform). However, if it hasn't (like in a celery worker), then
using mitxmako.middleware errors out.

[LMS-1085]
Update JS to reflect new link IDs to unbreak the top nav status indicator.
Verification: revises UI header copy
Verification: changes formatting of billing address/info on receipt view
adjusted payment option spacing, receipt page title and billing, and payment error page