Added the sonar pulse to reveal sub marines

As described in #4729 this was never implemented. Balancing wise I decided to make this a localized but multi-shot event similar to the spy plane. A good test case is http://resource.openra.net/maps/495/ which has creeps with an infiltratable sub pen and a submarine next to it plus soldiers that can be used as a disguise against the pillboxes.
If you wanted to follow that line of reasoning to its logical conclusion, then it would make sense to remove `SpyPlanePower` and `ParatroopersPower`, and have the generic `SpawnActorPower` define `DeliveryAircraft` and `ValidGround` parameters that match `CrateSpawner`.

I'm not asking you to do all of that - just to rename this to something sensible, which you have had no problems with doing in the past (#5305, #5359, etc).

#5724 requested a `RemoveAfterDelay` trait, and so I would like to see that used for the time part here, too.