User sees the average number of attempts taken for each graded and ungraded problem for learner group

[crathbun428]

User Story
As a course author, I want to see the average number of attempts taken to answer each problem in my course by the learners in my learner group, so I have another way to determine problem difficulty for those learners who may be at-risk learners.

Acceptance Criteria
Scenario: A course author sees the average number of attempts taken to answer each problem in the course by the learners in their learner group
Given I am a course author with X permissions
When I view the performance section of the learner group reports
Then I see the average number of attempts taken by learners in the learner group to answer each graded and ungraded problem in the course