[DO NOT MERGE] Atmos z level fix + radio controller code sanitization

Basically a placeholder before the feature freeze takes effect.

__What has been done :__
* Limit atmos/fire alerts to the current z_level
* Atmos/fire alerts are now linked to an object and not its area, as intended
* Simplified and full pathed the radio frequency datum
*  Made signaler properly clean on del/qdel

There's still some work to be done (notably on radio controller), before readying for merge