Allow players to choose between playermodels

I know this might seem excessive for the 0.1 board but it's the kind of thing that gets put off and forgotten forever if we never list it. I want to offer proper representation for our players, as soon as possible; you should be able to feel comfortably represented as either masc, fem or n/b when you're looking at yourself at the dealers and in the bar.

The bar itself is its own problem because talking to NPCs will be Trent's voice, which I imagine is a lot more work to deal with than the model. But just the model swapping would be a big W if we could get that in quicker. My ideal for now would be a basic choice between two helmeted spacesuit people in the Liberty style, and one of the bodies is more clearly feminine. Failing that, just having one Liberty helmed spacesuit person without any clearly defining features one way or the other would be acceptable.
Just anything better than asking our fem and n/b playtesters to always look like Trent would be meaningful.

The issue names no files, tests, or entry points. Start by locating how the current player model is assigned and where player choices are handled; done means players can select a masculine, feminine, or neutral-looking model, with the stated single neutral model as an acceptable fallback.

Written by the indexing model from the issue text.