Fix for Player Class and International Support

So to add a way of creating a good T/F check for player meta before
actually doing anything. Traditional isset() doesn't work on an object
like this since they're created via __get and __set, not actual
properties. So a pseudo isset was created wpRPG_Player->__isset( $name )
returns either T or F if the meta exists.

Also added international translation support. Basic attempts created for
english and german.