Changed str->unicode in common/djangoapps/utils/.

LMS-2436
Some more str->unicode fixes in instructor and courseware apps.

LMS-2429
Update doc string for YouTube stub server.

Included information on how to launch the server
on its own.
EOF
LMS-1287: Added section for batch add of beta testers
Merge pull request #3071 from edx/ahodges/documentation/bulkbeta

LMS-1287: Added section for batch add of beta testers
Support emitting analytical events from xblocks running in the LMS

XBlocks can and should use the "publish" method provided by the runtime to emit analytical events. In theory we could now start replacing calls to track_function with calls to publish, however, that migration is not handled by this change.

Fixes: AN-789
Reduce false cache misses when evaluating prerequisites
Merge pull request #3090 from edx/valera/update_youtube_stub_server_doc

Update doc string for YouTube stub server.
Make YouTube mocked server serve YouTube API

1.) Making YouTube mock server serve YouTube API.
2.) Adding ability to block YouTube API from YouTube mock server.
3.) Adding acceptance tests that check YouTube mock server for availability of YouTube API, and for it's ability to block YouTube API.

Part of BLD-939.
Merge pull request #3085 from edx/valera/make_youtube_mocked_server_serve_youtube_api

Make YouTube mocked server serve YouTube API
Add the ability to reorder Pages and hide the Wiki page.
Studio - revising markup, templates and styling for page editing UI:

* added in fixed state markup/logic
* added in collection markup/logic
* revised styling for page titles, collection, and fixed elements
Support for "View Live" on Pages page.
Settings for ENABLE_STUDENT_NOTES and ENABLE_TEXTBOOK in CMS.
Do not display empty collection tabs.
Updated Changelog.
Merge pull request #3064 from edx/nimisha/studio-reorder-and-hide-tabs

Nimisha/studio reorder and hide tabs
Merge pull request #3097 from edx/dcs/paver-reqs

Reduce false cache misses when evaluating prerequisites
temporarily remove SR on capa alerts to fix problem submissions (LMS-2474)
Merge pull request #3058 from edx/usman/lms2429-unicode-error-fixes

Unicode support fixes
fix raw grade dump in standard instructor dashboard
Added test and cleaned up code formatting
Review based changes
Converting class method and attributes to private
Remove unused methods from comment_client
Remove unused *args and **kwargs from perform_request