Check Cerberus firing at zero height

[GoogleFrog]

https://zero-k.info/Forum/Thread/38263?postID=269049

My guess would be that a weapon query point is at the base, so ends up "underwater", blocking line of fire. Cerb should be able to shoot everywhere it can be built, and being built at zero seems fine and consistent.

[sprunk]

Relatedly:

• all armed buildings (not just Cerb) should probably be able to shoot even when in reasonably shallow but unbuildable water
• perhaps some land-only buildings need to have their floating looked at for Quake/rez reasons (like Gauss was)? Not necessarily turrets, e.g. you can put singus underwater that way