EntityShootBowEvent

This adds the EntityShootBowEvent, which is triggered when either a player releases a pulled bow, or when a Skeleton shoots an arrow.

Outline:

Code:

class EntityShootBowEvent extends EntityEvent implements Cancellable {
    public Entity getEntity();     // returns shooter of the arrow
    public ItemStack getBow();     // returns the 'bow' item which was used to shoot, or null
    public Entity getProjectile(); // returns the arrow entity which is about to be launched
    public float getForce();       // returns the strength of the shooting; this is between 0.1 and 1.0, depending on the bow pulling time

    public void setProjectile(Entity projectile); // this allows to change the projectile which will be launched (can be null)
}

JavaDoc: EntityShootBowEvent
Bukkit commit: https://github.com/Bukkit/Bukkit/commit/d57776f058520cd38f5ba39831d1d53b59942211