modified edit question

- when a question, that did not have an evaluation period set, goes
into edit mode, the judge_start and judge_end datetime are initially
set. I have now initialized the values to be:

judge_start = answer_end
judge_end = judge_start + 14 days
updated participation report

- made the following changes
	- if a student did not submit an answer, they will be marked
	down as "No Answer" in the report.
	- if a student's answer did not get evaluated, they will get
	"Not Evaluated" instead of 0.
removed automatically adding the default criterion to course

- now that instructors can add their own criteria, we do not need
the system automatically adding the default criterion to the course.
implemented filter for questions on course home page

- also fixed saving dates in editing questions