secure-cookies: Allow to use secure HTTPS cookies (Django setting)

Cf https://docs.djangoproject.com/en/1.4/ref/settings/#std:setting-SESSION_COOKIE_SECURE
Make code more robust to bad input (for case where DB was populated with string None)
Increase randomness of course name in testcase
TNL-272: Fix double loading of cms-modules.js.
Merge pull request #5393 from edx/anton/js-double-loading-studio

Fix double loading of cms-modules.js.
Only execute regex queries for case-insitive lookup in split.

[LMS-11402]
Merge pull request #5396 from cpennington/split/specialize-regex-for-case-insensitive

Wrap get_item in bulk_operations to limit the number of queries for course structure.
Fix BulkAssertionMixin so that it actually asserts the truth/falsity of the contained assertions
Bump version of PyContracts so that it will disable the 'check' function
Teach mongo_connection to retry read operations in the face of AutoReconnect errors
Allow Timedelta and RelativeTime fields to handle from_json being passed timedelta objects
Put student profile third party auth behind a feature flag
Use split to test views
Fix acceptance tests to work w/ split
11300
Fix unit tests for generated
course ids.
Make xml exports more comparable by sorting and indenting json
Export xml from the destination store during cross-modulestore import/export tests
Make Studio CoursePage objects generate the correct CourseLocator based on whether the DEFAULT_STORE is set or not
Inherit from JSONField rather than Field for json-based fields
Merge pull request #5249 from edx/split/view_test_setup

Split/view test setup