Improve commission list functionality

[zkat]

I think we can definitely do better as far as how we display commissions. We should make it more obvious what commissions are in what state, what commissions have recent interactions, and probably make rejected commissions stop taking up so much room. It should be much easier to sort through your commission list, both as a client and as an artist, to find the thing you're looking for.

Some ideas:

• grouping by activity date (maybe at week-level granularity?)
• elevating some key filters out of the filter drop-down and into the main UI
• completely change how we do things and switch the artist view to be a Trello style board