Overlays

**(Do not merge yet.)**

This tracks the `overlays` branch and serves as TODO list. Contains color and animation overlays test code.

**To test, you will need fife git!** If necessary, use `--fife-path`.

Animation overlays
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See [Animation overlays] (https://github.com/unknown-horizons/unknown-horizons/wiki/animation-overlays) wiki article.

Color overlays
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Base image + image defining colored area(s) + color (bordeaux-ish) = ![towering-rogon](http://up.unknown-horizons.org/f/?a=v&id=474&n=2013_4-tower-overlay.png)

Supposed to be used for e.g. ships with flags in player color, ornaments at main square, ground units, etc.