Modified and added functionality to claim command.

- Changed '/claim release' to release all of a players owned worlds, and
not just the one they are currently on.
- Added '/claim list' to list all the worlds owned and indexed, which
can be passed to release to only release a given world, instead of all.
- Added '/claim who' to list the current owner of a world.
- Added field to store owners name in persistance claim data.