It would be nice to be able to use our own cache version in DefaultTileFactory.
DefaultTileFactory has a setTileCache, which is a good start.
We could extends from TileCache, but it has no accessors and the variables are
private so basically we have to redo the whole thing.
A default behaviour is great, but it would be nice to be able to overwrite some
In my case, I have the same APIs as in TileCache and I think it's a good start.
addToImageCache(final URI uri, final BufferedImage img)
put(URI uri, byte bimg, BufferedImage img)