Add /center commmand

src/main/java/com/sk89q/worldedit/regions/Region.java

@@ -44,6 +44,15 @@ public interface Region extends Iterable<BlockVector>, Cloneable {
      */
     public Vector getMaximumPoint();
 
+    /**
+     * Get the center point of a region.
+     * Note: Coordinates will not be integers
+     * if the corresponding lengths are even.
+     *
+     * @return center point
+     */
+    public Vector getCenter();
+
     /**
      * Get the number of blocks in the region.
      *