[miele] Add laundry weight channel for washing machine

[jlaur]

Seven years after finding water and energy consumption data within ExtendedDeviceState, I have now finally figured out the washing machine load shown in the app as "< 25%", "50%", etc.

By giving the sequence of bytes another fresh look while loading the machine, I discovered the two bytes holding this information, and actually it turned out to be the exact weight measured by the appliance.

Thus, I can now proudly present a new channel for exposing this information. Use-cases:

• The initially measured weight might make predictions about the water and energy consumption for a program more accurate, which will then improve automated scheduling for price optimization (e.g. when using Energi Data Service).
• This data might make it possible to warn when the machine is being overloaded, which will otherwise result in much longer program duration and water/energy consumption.
• Lost your kitchen scale? Worry not, use your washing machine and openHAB instead. Take care not to drop flour inside the appliance.

[lsiepel]

Thanks, LGTM