Fixed basic Survey access check.
Also enabled this check for all relevant Views. However ProjectSurveys and subclasses still need an additional check. A stub for this has been added to the access module.
Fixed showing the correct list of projects for taking a Grading Project Survey.
Note that when a user is a mentor for a lot of Organizations the amount of subqueries might exceed the allowed amount. A TODO has been added to fix this issue. However this will hopefully not be a problem that pops up soon.
Also some minor docstring addition to Project Survey view.