Added new config option 'load-chunk-on-request' in bukkit.yml.

This will be set to true by default until I fix all chunkloading issues
with this flag off.
Note: If you are experiencing performance issues and do not need any
chunks force-loaded, try disabling this setting.

* Added loadChunkOnProvideRequest for transferPlayerToDimension to fix
issues such as Twilight Forest's teleport not loading chunks properly
before spawn.
More "proper" fix for all the fun chunk loader issues
Added Naller's EntityItem.onUpdate logic (less jerky than Spigot's version)
Hack to stop mystcraft dimension spawn loading for 1.4.7