[WIP] Facility vehicles 002 fire_engine [CR]

Adds a smaller fire engine to accompany the large firetruck. 
Adds deluge guns as a deconstructible vehicle part. 
Makes the deluge gun a turret.
Fixes two deluge guns on the fire engine.
Makes fire engine spawn in some fire stations.

Justification: Didn't want to mess up the existing firetruck's layout by adding the guns and lots of water tanks, so put this one in.

Ok, pinpointed the error - using water as ammo is the source of problems. Now, how to define it properly...

Will be working on it tomorrow or the day after - have to take a flight today/tomorrow and might not have internet access immediately afterwards.
The first (closing) brace here closes up the function early.