Add spaceship loadout screen

[nstgeorge]

Allow players to determine stats about their ships, such as handling, acceleration, color, and name. Allow players to save their ships. This should be built later rather than sooner, so it can easily be integrated with scoring systems and new mechanics (like making the gun useful somehow). The logic for creating a ship is already there, so the main time consumer here will be designing the layout and UI elements to make this happen.

[rvanasa]

Specifically, we want to start by merging the PlayerShip and SpaceStation classes into the same underlying logic, since space stations have a much better customization system (StationLayoutContext).