Allow user-specified sorting of the scientists page

[fluffy-critter]

Right now users are sorted by username, which is counterintuitive and weird. It would be nice if the table columns had widgets for selecting the sort order instead.

[silby]

There are many tables X where "allow sorting of X" would be desirable and I encourage anyone in the future looking for a frontend task to pursue some kind of unified solution for this. Or rather two unified solutions, one for tables where every row is always on the screen and another for faceted searches.