Implement config-driven unlock groups so that multiple things can be unlocked at once (including buildings)

src/lib/config/ShipsConfig.h

@@ -35,10 +35,6 @@ struct ShipSensor
 struct ShipDef
 {
     std::string id;
-    int unlockAtStationLevel;
-    // Prerequisite schematic ids that must be explicitly unlocked before this
-    // schematic can enter the drop pool (REQ-LOCK-PREREQ). Empty = none.
-    std::vector<std::string> unlockRequires;
     std::vector<std::string> layout;
 
     ShipSchematic schematic;