Merge pull request #3952 from edx/clytwynec/prereqs_installation_update

fix for prereqs installation cache check
Merge pull request #3872 from edx/nick/disable-masking

Temporarily disable masking
Update EASE version (includes base reqs)
Update ddt to 0.8.0
Initial draft, need image and xrefs
Merge pull request #3956 from edx/adam/user-id-profile-information

adds user id to student profile information (LMS-2791)
Merge pull request #3959 from edx/will/update-ease

Update EASE version (includes base reqs)
Merge pull request #3934 from edx/flowerhack/handout-error-logs

Removed excessive logging
Skip intermittently failing test
Allow consumption of environment variables in docs Makefiles

See: https://bitbucket.org/birkenfeld/sphinx/issue/1368/makefile-options-not-overridable-from
Merge pull request #3963 from edx/zoldak/skip-video-seek-test

Skip intermittently failing bok-choy video seek test
Fixes BLD-1104
Extract i18n strings from *.underscore files using django-babel-underscore
Added completion and audio XBlocks
Move LS requirements to edx private.

Author/owner of change is Ned. Committer/typer is Piotr.
Code review changes from Ned+Cale
Add AI algorithm configuration to LMS settings

Added ORA2_FILE_PREFIX setting
Improve escaping in code response.
Added image, completed draft
Merge pull request #3964 from edx/benpatterson/auto-docs-builds

Allow consumption of environment variables in docs Makefiles