Add dither fade example

[gkjohnson]

Related to #297

TODO

• Don't fade in if tile is shown due to frustum culling change
  • Handled by hiding tiles that are not visible
• Is there a way to fade only on first load?
  • need to know when children have been removed and the traversal is awaiting a new load
• Detect high-speed cameras and don't fade in with high camera movement
• Consider searching for the fading in / out parent tiles and removing those in between / jumping the animation state
• Add potential cap of fade