First pass at the lightning gun code.

Haven't tried this in multiplayer, but it should be fun. You want to be
outside the water and shooting at someone in it. Mostly just a way to play
around with PARTICLE_TYPE_LIGHTNING systems.
sv_alternatespawns replaces the hyperblaster with the lightning gun in all maps. This is extensible so we can override a whole set of spawns in one lookup array.
custom pakfile

This contains the models and stuff for the lightning gun.
lightning gun behavior changes

now it arcs everywhere, but arcs farther and does triple damage in
water.
Merge branch 'lightning_gun' into particles