Update WebServer.py

Addsite.mc & bag.plist implementation based off of @dschuetz post here #37: https://forums.plexapp.com/index.php/topic/81972-installing-a-new-app-on-appletv-without-hijacking-trailers/page-2

Tested and works with plexconnect to give it addsite functionality for jailbroken atv2 ios 5.1+