Check state of group to see if anything is on

[GRX]

Hello,

I tried to make a branch (+ PR) to add a function to see if any light in a group is on rather than the whole group.
So instead of a PR here's the code :)

I've added it to Group.php:154;

/**
     * Is anything in the group on?
     *
     * @return bool True if on, false if not
     */
    public function anyOn()
    {
        return (bool) $this->attributes->state->any_on;
    }

[neoteknic]

Go on my fork please an make PR here :
https://github.com/neoteknic/Phue