Command update

Add a new command.

Command: dld_place
Permission: dld.place

This command will place a dungeon in the chunk of player.
Please be careful when using this command.
(1) This command will force the plugin to create a dungeon in this chunk. The dungeon is usually very big, so if there are some player-building structures, they'll be destroyed! And there's no way to undo it.
(2) The height of player's position will be ignored, as the dungeons will always under y=64.
(3) If you are trying to place a dungeon in an invalid position (like ocean biome or ender world), it will fail.