[iOS] Add Multipeer Connectivity functionality

Hi,

for now the ios plex app seems only to find devices that are on the same network. If í´m not at home, i often want to stream from one device with big storage to an other device with a larger screen. For now both devices need the same WiFi. But there are many situations without a open network. Like airplanes, cruises, tubes or holiday homes.

Apple has build a framework called multipeer connectivity to set up an easy way to communicate betwen devices without an open network.

It would be very usefull to integrate this into the ios plex app.