Improve rerun test

for troubleshooting TNL-692
Update wording per Doc
When s3fs cannot be accessed replaced with osfs
reorg of the receipt page header to match rest of the flow; removed cart-list class from receipt page wrapper
Updates to Demographics Display

- Gating on feature enabled for Open edX users
- If feature disabled and Insights URL is set, displaying message pointing users to Insights
Remove proxying of resources_fs, and add a unittest that exposes the problem

[PLAT-191]
Fixes for MOB-836 and MOB-766 and MA-96.
Correct test file path for bok-choy
Verify grade export works for problems in split tests

TNL-41
Merge pull request #5728 from edx/dan-f/grade-export-split-test

Verify grade export works for problems in split tests
Studio: visually styling current unit on course unit/container view's mini outline
Studio: correcting minor Sass indent and property syntax issues
Show current unit in unit outline.

TNL-291
Fix i18n and quality errors in course_groups/views.py
Studio: cleaning up/removing unused sass

* removing unused font-family-centric Sass variables
* removing unused graphic images and Sass references
* clean up of style removal fallout
deleting more things
courseware header bar should not overflow shopping cart button TNL-722
generalize draft import/export TNL-574

add test for videomodule

Import drafts handles modules w/o xml_attributes
and ones using the old parent_sequential_url pointer

Handle drafts for modules which don't define nor extract xml_attributes

Support  and  in get_items qualifiers

Unit test for   value query
Corrected link to Developer's guide

@mhoeber , @stroilova
Merge pull request #5769 from edx/ahodges/doc/DOC491

Corrected link to Developer's guide