v0.4.0

v0.4.0
-added Mk82 Bomb
-added AGM-114 Hellfire Missile
-added GAU/8 Avenger
-added Weapon Manager part
-added cannon shell blast power and radius config values
-new sound for Vulcan
-fixed explosionFX bug (explosion would multiply by how many parts it
hit)
-new large explosion fx for bombs
-temporarily disabled physics range extension by default
-tweaked missile guidance slightly