Rewrite tile calculations based on http://wiki.openstreetmap.org/wiki/Slippy_map_tilenames

Signed-off-by: Jody Garnett <jody.garnett@gmail.com>
Rewrite ivm developer works example of worker queue now that Doug Lee's concurrency library is included with Java. Make use of Java ExecutorService instead of coding this ourselves.

Signed-off-by: Jody Garnett <jody.garnett@gmail.com>