Updated ZombieMines

The map looks better now.

The barrel2 prefab's polygon collider had too many polygons, this was
causing the pathfinding to slow everything down. The number of polygons
has been reduced to fix this. It works *more* smoothly now.

To control the mine spawning we now use MineAreaSpawners. It's similar
to how another game project Botmines did their spawning, but should be
more simplistic.

Fixed a bug in the bulletMovement function as well.

Shotgun sound has pump action sound too.

Changed string in PauseMenu. Small change.

Changed rack's collider to box collider. I suppose it will help
efficiency in some small way. Little things add up I think.
Merge remote-tracking branch 'origin/master'

Conflicts:
	Assets/Scenes/ZombieMines.unity
	zed-reboot.userprefs