Edit section/subsection release dates and grading types.

Fix bok_choy test by changing course separator.
Change format of the modal title to '[Subsection/Section Name] Settings'.
Improve bok_choy test stability.
Studio: correcting modal window size name for outline settings editor
Specify full date in bok_choy tests.
Refactor bok_choy tests.
Remove .modal-editor from basic-modal.underscore
Set classes in modal window dynamically.
Studio: revising outline edit modal tip content and overall size
Rename isEditable to isEditableOnCourseOutline.
Interpolate display name.
Use graded instead of format as flag.
Studio: revising outline settings edit modal size
Fix selectors in bok_choy tests.
Merge pull request #4425 from edx/alex/edit_course_outline

Edit section and subsection at course outline page.