SpriteFrameCache: custom order option for :where

With this change you will be able to retrieve sprites from the Sprite Sheet
in an order that is not necessarily sequential and can show a single
frame several times in the animation.

Example:

    frames = SpriteFrameCache.frames.where prefix: "bear", suffix: ".png", order: [1, 5, 3, 5, 3, 1]

NOTE: I am not experienced with Joybox yet, maybe there is something already in place to achieve the same thing?