Marks up a weapon's view or world model with the attachment points the weapon fires from - the
muzzle, the shell-eject port, and so on - and plays the stock presentation off them: muzzle
flash, brass and tracer prefabs, plus the b_deploy/b_attack/b_reload animation parameters. Drop
this on a weapon model prefab, wire the attachment GameObjects, and override the On* hooks to
extend or replace any of it. The holding Sandbox.BaseWeapon drives it through those hooks.