Merge pull request #4376 from edx/ahodges/documentation/activestudents

New "Active Students" data on instructor dash
Added discussion label change to release notes
Merge pull request #4387 from edx/markhoeber/documentation/doc-748

Added discussion label change to release notes
Defensively checks that children exist in has_changes
overriding a few more log levels for acceptance tests
disabling zendesk in lettuce tests and removing help/feedback lettuce tests in favor of the existing JS ones
Disable failing video language test
Merge pull request #4393 from edx/zoldak/disable-video-lang-test

Disable failing video language test
setting default system to be lms
Merge pull request #4390 from edx/benmcmorran/defensive-has-changes

Defensively checks that children exist in has_changes
Pull out edX into variables in password reset email
Merge pull request #4395 from edx/mvo/unittests_alone

Setting default system to be lms in unittests
Testing for bugs off master for opaque-keys deprecation
Fixed some isinstance errors with opaque-keys
Removed some definition_key references
Switch offering to course and run
studio new style assumption corrections
Skip tests for location mapper

Since we're trying to get rid of location mapper,
skip these tests until we get rid of it entirely.
Fixed test that hardcoded url to deprecated format
Fix test_import and unicode issues.

Handle unicode in get_course_index