Implement Comexio-Smarthome

[nicoketzer]

This Implementation is Based on the Generic HTTP Worker (Pull Request #2098 )

As Noted in #2098 here is the first Component that uses the Generic HTTP Worker.

If there are changes to the main pull, I will transfer them to this pull request as well.

This Code is tested on my own Energy-Storage System and with my own Comexio-Smarthome-System.

Whats Implemented?

Relays can be read out and switched Current values can be read out Power values can be calculated by the given voltage and the read out current value. The total power (of all relays) is returned as "ActivePower" (SymetricMeter). The group prefix can be used to specify which unit is to be addressed (in the case of several units --> e.g. "IO-Server" and "IO-Extension"). Use with or without username and password (can be set in the Comexio web interface whether necessary or not and then adjusted accordingly in OpenEMS)