Add styling to due date and grading format of subsection.

Fixes https://openedx.atlassian.net/browse/STUD-2030 according to https://github.com/edx/edx-platform/blob/bulk-publishing/cms/templates/ux/reference/outline.html and https://github.com/edx/edx-platform/blob/bulk-publishing/cms/templates/ux/reference/outline_status_grading.html

Reviewers @talbs and @tymofij