Finish implementing jump gates

[flashgnash]

Jump gates were left half implemented (as I understand they were intended to allow a ship to jump from one gate to another instantaneously rather than having to travel there through space)

Currently, generating them is only possible via admin commands, and I'm not entirely sure how functional they are beyond a system for generating, storing and retrieving them

Needed:

• A way to build them in survival
• A way to power them (do they just use the ship's power or do they need their own power source?)
• Finish implementing the computercraft tui for selecting/using jump gates as it was left half finished and commented out