Added CommandExecutor, gave credit to cdncampbell

This commit has quite a few changes. I added the commandexecutor class,
which allows the player to type /pvp_restore to see all of the
information about the plugin, which isn't a lot right now.

Changed plugin.yml to reflect this.

Reformatted the playerlistener

Added the getCommand().setExecutor() method to onEnable()

Gave cdncampbell the credit he deserves :)