Mapping-ready AME

Created by: Efruit

• Adds a new subtype /obj/machinery/am_shielding/map which prevents the shielding units from generating warnings and deleting themselves if they fail to find other AME parts.
• Makes all AME shielding recursively seek out adjacent parts without a controller when spawned/constructed.
• Changes the "Refresh Parts" button on the controller to engage that seeking functionality, rather than just update the icons.