the update frequency of Victron MPPT charger data, the battery Soc, the
huawei charger power, and the power meter differ from one another, and
differ in particular from the inverter update frequency.
the OnBattery-specific data is now handled in a new method, outside the
upstream code, which merely call the new function(s). the new function
will update the websocket independently from inverter updates. also, it
adds the respective data if it actually changed since it was last
updated through the websocket.
for the webapp to be able to recover in case of errors, all values are
also written to the websocket with a fixed interval of 10 seconds.
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.
