Refactored the survey eval submissions page.

Deleted student_view_survey_evaluation_results because it was almost
identical to view_survey_results. There turns out to be no need to
separate the two.

Removed sub_id and chkbx_id columns from the survey_input table because
they weren't being used and always defaulted to null.

Removed saveSurveyEvaluation from the evaluation component since it's
been replaced by the stock CakePHP model save. The original hope was
that CakePHP's model save would automagically handle everything, but it
turns out that it couldn't make sense of the multiple responses possible
from the "Choose any of..." questions. Had to add some manual processing
to fix the data array to something that CakePHP likes.

There are two outstanding issues from this commit:

1. Some of the validation for access to do the evaluations could be
moved from the helper into the parent functions, since they're probably
very similar.

2. Students cannot modify their survey responses because the forms
aren't built to load previously submitted data. Note that this can be
fixed easily for all the fields except the "Choose any of..." multiple
response questions, which would probably require the reversal of the
manual processing I did to get model save to accept the data.