BLD-1117: Add read-only list of Group Configurations.
Add FEATURE['ENABLE_GROUP_CONFIGURATIONS'] and os.environ['FEATURE_GROUP_CONFIGURATIONS'].
Merge pull request #4267 from edx/tim/feature-group-configurations

BLD-1217: Create feature flag for switching Group Configurations editing on and off
Hide GroupConfiguration behind feature flag in cms/templates/settings.html.
Deleting a child of a unit should convert the unit to draft
if the unit is draftable but isn't yet draft.
Update translations (autogenerated message)
Clean up i18n paver commands
Merge pull request #4316 from edx/anton/group-experiments

BLD-1117, BLD-1217: Add read-only list of Group Configurations, Create feature flag.
Merge pull request #4314 from edx/sarina/070714-language-update

Sarina/070714 language update
Merge pull request #4315 from edx/bug/delete_draft

Deleting a child of a unit should convert the unit to draft
Replace unit page with the container page.

STUD-1754
New Publishing controls on Unit page.

STUD-1707
cleanup of unit, container, and xblock sass; added modules and layout sass; publishing states and actions on new unit
New publishing controls on unit page (continued)

STUD-1707
Adds warning when editing a container visible to students