Add Course Comparison dashboard to Superset

[crathbun428]

User Story
As a course delivery team member, I want to be able to compare either all courses/course runs on my instance or all courses/course runs I have access to, so that I can identify most and least popular courses and easily spot trends in enrollment, engagement and performance from course to course or course run to course run.

Acceptance Criteria

Given I am a user with Staff or Superuser django admin permissions
When I view the out-of-the-box reports available to me in Superset
Then I see a new Course Comparison dashboard report

Given I am an Active user in django admin
When I try to access Superset
Then I depending on if I have any roles in courses on my instance and what those roles are (see matrix here: https://docs.google.com/spreadsheets/d/1EWDn5V0o2WLZHsYdFe35SRgw7yekMMgAUuULnxRVV1A/edit?usp=sharing), I either can or cannot access Superset
And if I can access Superset
Then I see and open the Course Comparison dashboard and can only view information for the courses where I have an appropriate staff role on the Course Comparison dashboard.

Given I am an Inactive user in django admin
When I try to access Superset
Then I am not able to access Superset