fixed the inability to view students' survey

Previously if you are an administrator and have access to the course,
the system still returns an error message that it is an invalid id
when you are trying to access a survey. The reason is the system only
checks whether you are an instructor of the course or not. To fix this
problem, I have changed it to check whether the logged in user has
access to the course if they are trying to access the surveys not as
a student.
Fixed problem with exporting evaluation results to csv

I have discovered that when we export all results from evaluation
events that do not have the self evaluation option turned on, we
still receive rows of empty result for self evaluation.

For example, if we have no self-evaluation event and we exported all
the results we still get a row that have no results (as expected) for
Ed Student from Ed Student.
added a new permission called submitstudenteval

This permission is to allow or deny admins and instructors respectively
from submitting evaluations and surveys for the students