Projectile collision detection does not take height into account

[wraitii]

The projectile code does not actually care about height. PositionHelper.prototype.TestCollision does not compute the Y difference and doesn't care about the vertical footprint of the target.

Likewise, the aiming code in Attack.js just fires at the feet of the target.

Finally, ProjectileManager doesn't actually stick projectiles in the ground until _after_ they're supposed to have it, so projectiles are free to travel underground and hit anyways, and will "teleport" above if they fail to hit in those cases.