- Create new cohorts.py file
- moved code there from models.py
- implemented necessary functions.

Next: testing :)

- still needs style, more features, but basic functionality works

- lets user see and add cohorts
- needs styling
- needs to allow them to actually manage membership!

fix cohorts in create, and read, and update regular expressions to fix courses with periods not working in General commentable

Toggling of code should mark editor as dirty.

Do not run the lms jasmine tests on jenkins for now, until we fix them.

Fix/cdodge/remove hide progress tab

Feature/cale/fix staff debug link

studio - resolved bug with .header CSS inheritance and problem editor

staff_problem_info.html is only put on the page for staff, so we don't need to check staff_access inside it