fixed evaluation results' csv export filtering

Some fields were not being filter out correctly such as the final
mark and grades. The reason was the "filter" was checking whether
the index exist in $params; however they always exist (changes made
for version 3). Now the filters uses 1 & 0 directly (true and false
respectively). They no longer use the php functions isset or empty.
Some checkstye errors have also been fixed.
fixed rubrics eval form's comments check

The mechanism that checks whether all the comments have been answered
when comments are required was broken. This has now been fixed and
done in the controller instead of the view.
implemented a missing comments warning message for rubric

I have implemented a warning message that will come up when a
rubric evaluation is saved with missing comments when they are
required. I have also commented out the "validation" which
currently only returns true.
minor modifications

Commented out unused/deprecated functions from the evaluations
controller. The sql files have also been updated, to reflect
the removed functions from the evaluations controller.

I have also removed the extra '/' in the warning message in the
install controller. Another minor modification is the access model
test to reflect the changes made in the evaluations controller.