Refactor to builtin generic views where appropriate

[niklasmohrin]

Closes #1754

[niklasmohrin]

Linting is currently failing for some complicated views like UploadGradesView, I think I will just revert this one instead of trying to make the class based one work

[richardebeling]

Good stuff

[richardebeling]

Linting is currently failing for some complicated views like UploadGradesView, I think I will just revert this one instead of trying to make the class based one work

Overall, I'd be fine with having grade upload remain a function-based view. From the current CI linting output:

evap/staff/views.py:692:8: W0201: Attribute 'object' defined outside init (attribute-defined-outside-init)

I'd be fine with adding exceptions for these, i.e. telling pylint that dispatch (and, if necessary, form_valid) may define new attributes.

evap/grades/views.py:116:4: W0221: Number of parameters was 4 in 'View.dispatch' and is now 3 in overriding 'UploadGradesView.dispatch' method (arguments-differ)

Why is that? What additional two arguments does View.dispatch offer? Couldn't we just also take *args and **kwargs and simply pass them on?
(similar thing for get_object)

[niklasmohrin]

Lints are all fixed, reverted some views to functions, FormSetView now has more niceties

[richardebeling]

Looks good at a quick glance, but I'll have to go through it carefully once more. You can rebase / prepare a merge if you want.

[Kakadus]

I think the forms are definitely more readable now