Add quick check of the final answer for problems where most of the class got the same answer on the graph summary

[jaltekruse]

The assumption with the graph summary is that problems sorted to the right should likely be problems where all students got the right answer. This should often be the case, but it can also represent cases where there are common misunderstandings caused many students get the same wrong answer. A way to quickly verify this answer against an answer key, without having to click on each problem would help identify these cases. A mouseover on the graph could include the final answer reached by the largest number of students.