Added hitsounds

Cvars added:

cg_hitsounds (default 1)
  enable hitsounds client side

cg_hitsoundsCritical (default 0)
  0 or damage percent required to play the critical hit sound

g_hitsounds (default 1)
  0 - off
  1 - humans only
  2 - humans and aliens

g_hitsoundsType (default 1)
  0 - hit count
  1 - hit damage

g_hitsoundsFriendly (default 0)
  enable hitsounds for friendlies

g_hitsoundsBuildable (default 0)
  enable hitsounds for buildables

Co-Authored-by: Jeff Kent <jeff@jkent.net>