balance tweak - make turret armor heavy

Since turrets have wood armor, they can get killed by flame tanks uber fast. It might be best if turrets are a counter to flame tanks, rather than their prey. If they have heavy armor, they will take far less damage, and not die instantly to a flame tank rush, making them able to contribute to some defense.
Adjust air strike so it kills turret

The recent armor change for turrets made airstrike no longer killed it. 

Made Napalm do more damage to Heavy (and light); made Vulcan do less damage to Heavy so that airstrikes don't do too much damage to advanced towers, obelisks and SAM sites.
Merge pull request #5186 from psydev/patch-7

balance tweak - make turret armor heavy