Fix reading dungeon files (#899)

Now requires new rooms to be registered in `resources/assets/bloodmagic/schematics/Schematics.json`. This *can* be overwritten by a resource pack, so adding new rooms is still possible. Also allows sub-folders, so sorting rooms is now possible (sort by themes maybe?)

src/main/java/WayofTime/bloodmagic/structures/ModDungeons.java

@@ -23,6 +23,6 @@ public class ModDungeons
 //
 //        DungeonRoomLoader.saveDungeons();
 
-//        DungeonRoomLoader.loadDungeons();
+        DungeonRoomLoader.loadDungeons();
     }
 }