Metaworlds Mod

- added an administration gui (command "/mwc") to spawn/despawn and teleport subworlds - added a world/subworld importer to import subworlds or the main world from the same or other savegames and add it as a subworld to the current world. The importer is accessible through the administration gui (command "/mwc") - fixed entities/camera jittering when the subworld is being controlled - fixed the subworld controller hovering the player too high in the air while taking control - fixed the reintegrator block to prevent contagious subworld creators from immediately turning the structure back into a subworld