Allow access to decrypt/encrypt sounds so we can replace default voices and add additional callsigns

[TEMPEST.114]

as the title says.

This used to be possible until you encrypted the audio - If we could have the tool to decrypt/re-encrypt we can add new callsigns, change pilot voices etc.

This would be a huge win for mission designers.

[Rudel_chw]

ED encrypted those for a reason, why would they now move back just to grant a wish?