Makes secure electronics printable, airlock cleanup

* Makes secure airlock electronics available from the circuit imprinter
* Merges the secured_wires and secure_bolts vars, and gets rid of the latter. This way players have the option of making secure doors if they can get the electronics.
* Removes the icon_state hack
* Moves airlock electronics creation into it's own proc
* Moved airlock creation from a door assembly to airlock/New()