make embargo template theme-able

Use "Stanford-style" theming to enable you to put your own embargo
notice up.
missing themed embargo page fails safely to unthemed
updated pdf viewer
Add some optional policies around password resets, such as password reuse, forced password resets, allowed frequency of password resets
password history: just limit the result set range to simplify iteration logic
Fix flaky acceptance test.
Fixed studio can't handle more than 9 lines in advanced settings.
STUD-1483
Remove unused function
Centralize when json parsing of responses from controller_query_service happens
Fixed nested bullets to enable PDF

4 levels of bullets don’t work with latex

DOC-250
Fix a decode error in course_about.html and make some string translatable

The strings in share links should be in unicode, otherwise when the name of a course is non-ascii, it will generate a decode error.
And some of these strings is actually translatable, so they should be collected into mako.po.
Improve inline discussion UI

1. Add space between threads
2. Change Show/Hide to Expand/Collapse and visually separate it
3. Limit a thread to 700px high and scroll if longer

Co-authored-by: marco <marcotuts@gmail.com>
Fixes LMS-2474 by ensuring that readElts reads always reads an element
Emit datadog events for all course enrollments, not just those outside of verified courses
Merge pull request #3110 from edx/gprice/inline-visual-fixup

Improve inline discussion UI
Merge pull request #3134 from edx/dcs/a11y-gentle-alert

Fixes LMS-2474 by ensuring that readElts reads always reads an element
Merge pull request #3157 from edx/markhoeber/documentation/PDF-fix

Fixed nested bullets to enable PDF
Collect metrics around the open_ended_grading controller_query_service
Correctly catch RubricParsingErrors
Make GradingServices always return dictionaries, rather than sometimes returning strings