Add scoreboard filter

[Leonabcd123]

Fixes #688

NOTE:
I'm having some problems with self hosting, so I wasn't able to test any of this code. For that reason (and because I suck), I didn't write the frontend for this (although it should be just a simple select element, and then we can assign its value to current_filter).

[ConnorNelson]

I don't think this is the correct approach. With the exception of showing a fork for asu emails, we do not want special asu-specific code in the dojo.

The correct way to do this sort of thing would be to check if they are a member of the dojo (e.g. DojoMembers or DojoStudents), and probably more specifically if there is an official roster of students for that dojo, only considering those students. But then we'd also need to make sure we don't reveal that roster. I'd want to see all the edge cases of this considered.

Also, unfortunately we cannot merge untested code. For example, your indentation here is incorrect.

[Leonabcd123]

So just to make sure before I go any further, we want to only let the official roster of students see the scoreboard that contains only their classmates?