Improvements to Sprite Player

Hello hello. I've made the following improvements to the Sprite Player:

• You can now select frames to animate, useful for just playing a specific animation
• Added background color selection
• Added cell numbers, useful when you are looking for the set of frame numbers that plays a specific animation
• Performance improvements, everything should just load a tad bit faster now

Once again, your thoughts are the secret recipe to making Sprite Player better for everyone and I'm happy to consider implementing them over time.