make unit tests respect mongo port/host settings (with default)

settings are read in from environment variable
Properly (de)serialize references in old mongo
LMS-11204
set root logging level for acceptance tests to ERROR
Use English for the marketing site buttons in an edx-controlled domain
Update i18n-tools
Merge pull request #4842 from edx/will/ecom-90

Use English for the marketing site buttons in an edx-controlled domain
Auto enroll students even if there are multiple course modes

Add session middleware to an external auth test to fix a test failure with the auto-registration AB-test changes
Template changes for course track AB-test
Merge pull request #4748 from Stanford-Online/jbau/parallel-unit-tests

make unit tests respect mongo port/host settings (with default)
Merge pull request #4846 from edx/db/update-i18n-tools

Update i18n-tools
Add a request-token to identify which xblock html was rendered as part of the current request

[STUD-2903]
Merge pull request #4824 from edx/will/auto-register

Auto enroll students even if there are multiple course modes
Sync children vertical names with group names in split test module.
Merge pull request #4853 from edx/christina/stud-2093

Add a request-token to identify which xblock html was rendered as part o...
Merge pull request #4838 from edx/clytwynec/remove_warnings_from_lettuce_test_logs

set root logging level for acceptance tests to ERROR
Merge pull request #4777 from edx/anton/sync-groups-and-verticals

Anton/sync groups and verticals
Instructor Dash: Display message when there are no tasks running

This commit adds a message to the instructor dashboard that is displayed when
no instructor tasks are currently running. This message is displayed where the
instructor pending tasks table would normally be placed, and is replaced
with the table when there are running tasks.
Merge pull request #4848 from Stanford-Online/njdupoux/no-pending-instructor-tasks

Instructor Dash: Display message when no tasks running
XML export maps keys into xml expected format
Merge pull request #4803 from edx/dhm/import_split_test

Dhm/import split test