Bukkit

V 0.4

    * Added scheduler functionality.

V 0.3

    * Moved execution of backup script to seperate thread to avoid blocking
    * Added status messages that can be broadcasted

V 0.2

    * Command 'backup' works.

V 0.1 - Initial

    * Basic structure

The same backup job can run concurrently - causing race conditions.
A scheduled backup requiring players only runs if players are logged in the instant the job executes. Will be changed later to run at least once after the last player signs out.