Make sure temporary course directory uses safe characters.
Only permit ascii characters in filenames generated from course_ids.
Don't show cohort information when disabled

TNL-552
Address code review comments
Minor cleanups
Merge pull request #5517 from edx/brian/fix_export_course

Make sure temporary course directory uses safe characters.
Merge pull request #5501 from edx/andya/disable-cohorts-ui-bug

Don't show cohort information when disabled
Small changes to the segment.io event handler
Updates 10-7 release notes
Merge pull request #5537 from edx/sylvia/docs/relnotes10-7

Updates 10-7 release notes
Merge pull request #5527 from mulby/tweak-segment-io-endpoint

Small changes to the segment.io event handler