[TEAMMATES#9230] Release V6.15.0 (TEAMMATES#9231)

[TEAMMATES#8957] InstructorCourseDetailsPageUiTest.testRemindAction f…

…ailing on live server (TEAMMATES#9171)

[TEAMMATES#9182] Release V6.13.0 (TEAMMATES#9189)

[TEAMMATES#9141] Release V6.12.0 (TEAMMATES#9142)

[TEAMMATES#9100] Release V6.11.0 (TEAMMATES#9108)

[TEAMMATES#9007] Rubric questions: allow weight for each cell: Migrat…

…e legacy data into new format (TEAMMATES#9047)

[TEAMMATES#9034] Student: Comment on responses: Fix put document error (

TEAMMATES#9035)