[mercedesme] Websocket decoupling

[weymann]

Warnings from MercedesMe websocket reported in community, After analysis design flaw in current binding needs to solved: Websocket thread is performing the complete chain from reading bytestream up to channel updates. While this other messages are dismissed Structural change to free websocket thread as early as possible:

1. Websocket thread responsible for reading stream in bytes and enqueue for AccountHandler.
2. AccountHamdler thread responsible for encoding proto message. In case of update enqueue proto message at VehicleHandöer
3. VehicleHandler responsible to update channels