allow to configure when which schematic gets unlockable

src/lib/config/ConfigLoader.cpp

@@ -403,7 +403,7 @@ ShipsConfig ConfigLoader::loadShips(const std::string& path)
 
         ShipDef def;
         def.id                 = requireString(mt["id"],                 file, elemPath + ".id");
-        def.availableFromStart = requireBool(mt["available_from_start"], file, elemPath + ".available_from_start");
+        def.unlockAtStationLevel = static_cast<int>(requireInt(mt["unlock_at_station_level"], file, elemPath + ".unlock_at_station_level"));
         def.layout             = requireStringArray(mt["layout"],       file, elemPath + ".layout");
 
         // Schematic

src/lib/config/ShipsConfig.h

@@ -51,7 +51,7 @@ struct ShipLoot
 struct ShipDef
 {
     std::string id;
-    bool availableFromStart;
+    int unlockAtStationLevel;
     std::vector<std::string> layout;
 
     ShipSchematic schematic;