space station: prototype

[0xDE57]

Add a space station that orbits either a star or planet.

Initial Implementation:

~~- [ ] better texture/sprite (one that actually looks like a space station)~~ moved -> #42

• [x] orbits around a planet or star
• [x] ships can dock at space station when near
  • [x] sensor for docking locations
  • [x] action/keybind to dock/undock
  • [x] auto-undock when engines applied (no need for explicit keybind)
• [x] sell cargo for moneys
• [x] repair ship (small cost)
• [x] player will spawn here at game start and when die, instead of in middle of nowhere -> #18
• [x] UI element to show docking port area
• [x] dock / undock sound fx -> #12 ~~- [ ] save game (auto save when dock? or put a save button in station UI?~~ #43
• [ ] last docked station becomes spawn point

Later:

~~- [ ] IK arms to grab ship~~ -> #42 ~~- [ ] upgrade ship~~ -> #43 ~~- [ ] buy/sell ships~~ -> #43