LWC support, Refresh Biome, Fix Clear

- Refactored the MinecraftFontWidthCalculator class
- When plot is cleared, removes LWC locks
- When plot is cleared, removes entities : Will need to put options on
this so people can set what type of entities to remove (living too?)
- When plot is cleared, containers are emptied : Also make this an
option
* Issue with jukebox, cannot remove the CD, can only eject it. Is an
issue with Craftbukkit, made a ticket here :
https://bukkit.atlassian.net/browse/BUKKIT-3429