Prevent reflected XSS in instructor dashboard.
Use display_name_with_default instead of display_name.
Increase max-width for breadcrumb trail.
Improve code clarity.
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 #2807 from edx/christina/containers

Support xblocks with children on the container page.
Fixes tinymce bug:
    On using the image plugin, the image was not appearing in the
    visual editor immediately after using the command.

    Selenium test added.
making mixed ms capable of front ending all modulestores for most operations including CRUD
STUD-600
Merge pull request #2824 from cpennington/rc-ab-tests

A/B Test Module
Mixed no longer translates
unicode correctly and understandably
Pass user id to update_item
Point to prefer_xmodules new locn
Better sorting of stores for get_courses
May apply to all store ordering
Mixed modulestore handles most modulestore functions, cont.
Change get_courses default branch to draft.
We need to figure out how apps configure what default they want or ensure they get the one they want
No longer create loc maps on create_(item|course)