Move Bluetooth to L2CAP

[decanus]

We currently use the more high level bluetooth API. We should change this to the more low level L2CAP api. This will require writing generic streams that can be used by other transports too.

Notes

• https://github.com/paulw11/L2CapDemo
• https://developer.apple.com/videos/play/wwdc2017/712/

[decanus]

won't work on cause android does not expose this API.