fixed unscored answers appearing on top

I've modified a  custom filter found at the link below:
http://stackoverflow.com/questions/18604374/angularjs-orderby-with-empty-field

It appends the unscored answers to the end of the scored answers
implemented two minor features

- only show answers to users after they have submitted an answer
- only let a user to submit one answer per question

I've also fixed the buttons on the course home page.
Implemented "required N judgements" counter on course home page

I have implemented a "counter" for number of required judgements
left for the user to complete. It is currently labeled as
"Judgements Left".

The required number of judgements per user is calculated by:

x = required # of rounds per pair = 6
y = minimum # of pairs of answers  = # of answers / 2
required # of judgements = (x*y) / # of students