Add two tabs to the Course Comparison dashboard

[crathbun428]

**User Story **
As a Course Operator, I want there to be two tabs at the top of the Course Comparison Dashboard (one for Course Metrics and one for Course Run Metrics), so that I'm able to decide and toggle between viewing aggregate course information or individual course run information as a basis of comparison depending on the data I need.

Acceptance Criteria
Given I have access to the Course Comparison dashboard
When I view the Course Comparison dashboard
Then I see two tabs at the top: Course Metrics and Run Metrics
And I see the default tab when I open the dashboard is Course Metrics and shows aggregate metrics for an entire course
And when I click on the Run Metrics tab
Then I see the same tables and charts, but the numbers represent the counts for individual course runs

UX/UI Direction