BETA: Admin Clan commands rework.

    * Command clan_changeleader won't do numeric exceptions.
    * Now is possible to use the name of the character, clan_changeleader Zoey76
    * Removed custom system messages, used available in client (Unharcoded).
    * Removed iteration over clan members, this should improve command performance.
    * Removed e.printStatckTrace(), replaced with proper logger.
    * Implemented off-line privileges set for former clan leader.
    * Better handling of exceptions.
    * Cleanup and code formatting.