Restore boarding parties.

[DaloLorn]

• [ ] Illyia suggested a channeled ability instead of a one-off 'fire and forget' ability. This is a good idea, but we need to flesh it out a bit more, figure out where we want to go with it.
• [ ] Implement the new boarding system.
• [ ] Optionally also implement issue #24 for synergy, or revamp the repair system so people can shoot out a ship's engines to keep it from escaping.
• [ ] Maybe prevent people from shooting at ships they're boarding, and prevent boarded ships from shooting at the ship that's boarding them?

[DaloLorn]

This is done. Not quite the way it was described above, but it's done.