This commit updates lms/templates.

These keys are now objects with a limited interface, and the particular
internal representation is managed by the data storage layer (the
modulestore).

For the LMS, there should be no outward-facing changes to the system.
The keys are, for now, a change to internal representation only. For
Studio, the new serialized form of the keys is used in urls, to allow
for further migration in the future.

Co-Author: Andy Armstrong <andya@edx.org>
Co-Author: Christina Roberts <christina@edx.org>
Co-Author: David Baumgold <db@edx.org>
Co-Author: Diana Huang <dkh@edx.org>
Co-Author: Don Mitchell <dmitchell@edx.org>
Co-Author: Julia Hansbrough <julia@edx.org>
Co-Author: Nimisha Asthagiri <nasthagiri@edx.org>
Co-Author: Sarina Canelake <sarina@edx.org>

[LMS-2370]

The button text default is now in the template and i18n-able, a
PROGRESS_SUCCESS_BUTTON_TEXT_OVERRIDE option is offered in settings.
The button url now uses string formatting.

Show a button at the top of lms/templates/courseware/progress.html if the
lowest nonzero grade cutoff has been reached. Introduce two settings:
PROGRESS_SUCCESS_BUTTON_URL is the href of that button (the course id is
appended); PROGRESS_SUCCESS_BUTTON_TEXT is the text, defaults to
"Download your certificate"

Currently just coerces the time displayed for due dates
(accordion.html and progess.html) to settings.TIME_ZONE

LMS-2156

Added verification sidebar, banner for major courseware sections, quality & test improvements

Hide show_timezone from Advanced Settings and migrate courses with show_timezone=False to using due_date_display_format.

STUD-724

Test course for allowing custom formatting of due date strings.

STUD-724

Try making the name of the course match the folder name.

More cleanup.

More cleanup.

updates.

lms - adds back in missing/previously added .sr screen reader-focused styling and references in place of the .visuallyhidden application

courseware active location, suppress browser form validation, and progress graph accessibilit changes