Fix: station shops
Station shops stock gear again, varied per station.
- Fixed station shops showing no gear; weapons, shields, thrusters, generators and scanners are buyable again.
- Changed shops to stock per station, so each one carries a different selection of gear.
- Changed industrial shops to stock part of the base-building catalog, not every base core and part.
- Changed stations to fly the flag of the faction that owns their system; stations in unclaimed space are independent.
- Removed the gear shop from about 1 in 10 stations.