Allow courses to set Matlab API key globally, in advanced settings.
Updated payload for new matlab endpoint.
Don't hardcode https protocol in enrollment emails.

Use http or https, depending on the value of `request.is_secure()`.
That is how links in most other emails are handled.
Ensure no old gems are left behind between test runs.
No longer chunk queries when sending out bulk email (LMS-2718)

refactor _generate_items_for_subtask not to chunk queries

use django's iterator methor for querysets

remove bulk email query settings

use read_replica if available, since this is read-only

update changelog
Annotation Tools: Load Tinymce in student_view
Annotation Tools: Fixing tests for student_view

Fixed typo from autocomplete

Fixed dict for tests
Updated version of event-tracking library to 0.1.0
Update help for welcome, register, and login pages

All now go to getting started, but have different tokens, for further
segmenting later.
Welcome page text edits
Merge pull request #3841 from edx/fix/large-email-queries-2

Fix/large email queries 2
Move to OpaqueKey implementations from the external library

[LMS-2757]
Fix the title of edit modals from the unit page.
show a friendly message for an empty course rather than an error page
Fix location.url [LMS-2786]
Merge pull request #3931 from edx/sarina/fixup-external-opaque-keys-impls

Use external OpaqueKey implementations
Merge pull request #3929 from edx/sarina/lms-2786

Fix location.url [LMS-2786]
Merge pull request #3754 from theJohnnyBrown/empty-course-error

show a friendly message for an empty course rather than an error page
Add span tag.
Merge pull request #3917 from edx/oleg/add-span-tag-matlab

Accept span tag from xqueue. BLD-1006.