Support GATT services over BR/EDR.

Preview at https://rawgit.com/WebBluetoothCG/web-bluetooth/support-bredr/index.html

@armansito
Let's keep this to a separate patch, but it sounds plausible. Since the website needs to communicate using services anyway, I'm inclined to insist that it list the services it's interested in, but the rest of the fields might tell the UA to go through the whole connect&discover dance.