Add ability to specify a .tar.gz or .tgz file containing a world to be extracted cleanly on every server start with the force-map config option.

Please note: the archive is extracted directly into the folder returned by Bukkit.getWorldContainer() which should be the main directory unless otherwise specified. It will also attempt to delete the 'world', 'world_nether' and 'world_the_end' folders BEFORE extracting.