Make forum comment buttons activate by keyboard

Neither edit nor delete activated on pressing the space key.
making LMS modal buttons more flexible to handle longer strings in translation, eg. French
Merge pull request #2805 from edx/gprice/comment-edit-button-key-activation

Make forum comment buttons activate by keyboard
Merge pull request #2806 from edx/frances/fix/lms-modal-button

making LMS modal buttons more flexible to handle longer strings in trans...
updating commit
Merge pull request #2817 from edx/jarv/update-js-draw-commit

updating commit
Allow HTML in grader messages.
xblock-mentoring: Add repository to requirements & installed apps

Adding to installed Django applications is required due to the use
of a Django model by the XBlock
Activate XBlocks by default in LMS & Studio
Merge pull request #2814 from gsehub/xblock-mentoring

xblock-mentoring: Add repository to requirements & installed apps
Merge pull request #2818 from edx/alex/allow_html_in_grader_msg

Allow HTML in grader messages.
Prevent reflected XSS in instructor dashboard.
split testing support in the LMS.

Adds a split_test_module XModule, that can choose one of its children
to display, based on a get_condition_for_user API added to the runtime.

To test, add something like this to an xml course, or make equivalent
 tweaks in mongo.

 <vertical url_name="split_test_vert">
    <split_test url_name="split1" experiment_id="0" condition_id_to_child='{"0": "i4x://MITx/6.00x/html/split_test_cond0", "1": "i4x://MITx/6.00x/html/split_test_cond1"}'>
       <html url_name="split_test_cond0">condition 0</html>
       <html url_name="split_test_cond1">condition 1</html>
    </split_test>
  </vertical>

Also needs an experiment configured in the course policy json: e.g.

        "user_partitions": [{"id": 0,
                                      "name": "Experiment 0",
                                      "description": "Unicorns?",
                                      "version": 1,
                                      "groups": [{"id": 0,
                                                        "name": "group 0",
                                                        "version": 1},
                                                        {"id": 1,
                                                        "name": "group 1",
                                                        "version": 1}]}]

(This particular snippet will work inside a course with org MITx
 and course name 6.00x)

Co-Author: Sarina Canelake <sarina@edx.org>
Co-Author: Julia Hansbrough <julia@edx.org>
Co-Author: Diana Huang <diana@edx.org>
Co-Author: Calen Pennington <cale@edx.org>

[LMS-2095]
Add course tags to all events where a course-id can be extracted from the url

[LMS-2105]
Track renders of split_test children

[LMS-2098]
Add tests and clean up A/B testing

Also fixes STUD-1351
Merge pull request #2824 from cpennington/rc-ab-tests

A/B Test Module
Merge remote-tracking branch 'origin/master' into release, conflicts resolved

Conflicts:
	cms/envs/common.py
	common/lib/xmodule/xmodule/seq_module.py
	lms/envs/common.py
	requirements/edx/edx-private.txt
Merge branch 'release'