Dynmap integration

* If Dynmap is installed on the server, and the feature isn't disabled
in the config, CraftZ will now display markers on the map. Supported are
loot chests, player spawns, and the world border.
* Zombies and players now spawn at the center of the block, instead of
at its corner.
* Join/Quit messages with colored usernames now behave correctly.
* A huge part of the code revolving around chest refilling and zombie
spawning was optimized.