Rewriting permission system to use UUIDs and Ranks

As outlined in the forum http://forum.mc-server.org/showthread.php?tid=1540 , this PR changes the permission system to use UUIDs instead of playernames, and at the same time is refactored to use SQLite for the storage, and an entire new set of API for management.

Do not merge yet, this is work in progress, PR-ed for discussion purposes.
Unchecked return value