User sees a breakdown of learners by enrollment track (of the enrollment tracks available on user’s instance)

[crathbun428]

User Story
As a course author, I want to view a breakdown of the learners by enrollment track available on my instance, so that I am able to view and compare the enrollees in the learner group against all the enrollees in my course.

Acceptance Criteria
Scenario: A course author sees a breakdown of learners by enrollment track for their learner group
Given I am a course author with X permissions
When I view the learner group reports
Then I see a breakdown of the number of learners per enrollment track on my instance for my learner group
And I see a breakdown of the percentage of learners in my learner group in each enrollment track on my instance (so its easy to compare to course-level learner enrollment data)