Bukkit

- Added map saving. Finally, the changes you make to maps will save to disk and persist through a server restart.
- Added a new map type: "hostiles" with no arguments. This displays blocks that are capable of spawning mobs; red indicates underground areas, and yellow indicates above ground. (Underground takes priority.) Adjusts with daylight too, so you can check the map at night and see the difference.
---- Note that this is very intensive, and thus updates *very* slowly on purpose to avoid thrashing servers. Let me know if it's causing issues and I'll tone it down some more.

- Maps are sometimes failing to save to disk immediately after a modification is made. This isn't a huge issue so long as the server closes cleanly, but it might cause loss of modifications in rare instances when the server crashes after changes are made. Not sure how to fix; it's random, and seems to be caused by file handles not flushing quickly enough after a delete. (Anyone experienced with java file io want to take a crack at this?)