adding ImpactSounds to many weapons + other changes

When I recently watched the new desert shellmap, I felt something was missing somehow. I soon realised there where sounds of guns firing and missiles launching, but barely any noticable explosion sounds. Not surprising, considering most weapons had no ImpactSound defined at all.
In addition, I felt not just the impact sound, but also the explosion animation of artillery and cruiser grenades was too unimpressive.

With these changes, most weapons using visible projectiles gain an impact sound, while artillery shells use the larger art-exp1 and use kaboom22 as impact sound.