Keba-kecontact

fix set_charging_power by adding default delay of 1 sec

code style improvements
adding thread safe singleton
fix service calls

Fix: run init_socket only once

Breaking changes:
- Renamed "Wallbox" to charging station in all parts of this library. Wallbox is commonly only used in German language

Improvements:
- Rewrote backend to handle discovery and fetching device in a synchonuous way (waiting for response)
- Introduced enums for KebaService and KebaResponse types

small improvements and fixes

Adding BMW Wallbox Connect as model
allow 63A for charging power
small fixes