Refactor image asset loading to support all operations

[blixt]

Images can have several operations applied to them:

• [x] Hue shifting
• [ ] Saturation
• [ ] Brightness
• [ ] Color fade
• [ ] Masking
• [x] Color replace

These operations are generally defined in the path to the image:

/parallax/desertback2/base/3.png?hueshift=-26?brightness=18?saturation=-12?fade=ffffff=0.3

Some of this functionality is currently supported for tiles (hue shifting), but should be generalized so that it can be used for all types of images (parallax images, object images, plant piece images, NPC images, etc.)