Add Support For Marker Bitmaps

[bleege]

Now that the setSprite() issue has been resolved we need to add support for custom images (aka Drawable) in the Marker API.

[ljbade]

@bleege I have already implemented this via Marker.setIcon(Sprite icon). I called it setIcon to remain consistent with Google Maps.

To get a Sprite you call one of the SpriteFactory.fromEtc(etc) methods. There isn't one for a Drawable but we can add a fromDrawable easily.

[ljbade]

I added a fromDrawable.

I used it in the InfoWindowAdapter activity to add colored city markers that match the color of the InfoWindow.