modified self-evaluation redirect

- if the user did not submit an answer, they will be redirected back
to the course home page. The reason is it does not make sense for them
to proceed to the self evaluation since they do not have an answer to
reflect on. Also the form would not work since there isn't an
answerId to attach to the comment.
minor enhancements to the evaluation process

- redirect the user back to the course home page when they try to
proceed to self-evaluation without submitting an evaluation previously
- added computation for the logic to determine whether there are enough
answers to generate enough pairs for the user to complete the required
number of evaluations.
	- the warning message is currently in the same warning label
	as the one that tells the user how many evaluations they
	have left to complete. I assume we would want to move this.