added overview to results_course_detail page

This fixes #344.

The course's results pages now have an additional overview box that again shows the information from the semester overview page.
Also, "Lecturer" was changed to "Responsible" on the results pages.

A screenshot: ![overview_box](https://cloud.githubusercontent.com/assets/1781719/3562838/dfd4a6ca-0a0d-11e4-9efd-a9849c2a8e3a.PNG)