Fix CCMenu alignment with anchor

Hi,

with this PR `CCMenu` will no longer ignore the current anchor point in `alignItemsVerticallyWithPadding` and `alignItemsHorizontallyWithPadding`.

This bug exists in cocos2d-iphone too and parts of this PR are based on [this thread](http://www.cocos2d-iphone.org/forum/topic/8261).

Best regards, Michael