Add: Ability for Wifi Shield to be server rather then client

[MobileRez]

Reason for feature: phones and other devices are not always able to be set up as the server for the shield to communicate with.

Reversing the roles and configuring the shield to be the server rather then the client, would enable those devices to retrieve info from the WiFi shield without the means of a intermediary devices like a Raspberry pi or some other option adding more hardware to the mix and making it harder to pair multiple WiFi shields with devices on networks or even preventing those devices from being stand alone without the use of a intermediary device.