To reduce the heap usage it is necessary to send the inverters one by one instead of a huge response. A simple call to `/api/livedata/status` returns just some very general information. If detailed inverter information are required the inverter serial number has to appended `?inv=<serial number>`.
The websocket also returns only one inverter at a time. It as to be assembled at client side.
Added additional field to the prometheus api which identifies a channel by it's type. That means that e.g. channel 0 exists for type AC and DC.
This commit also introduces a additional field in the statistics byte assignment table. This field identifies whether a channel is on the AC or DC side. MQTT and WebAPI is still compatible with the previous design.
