Align Environment/Weather/CloudState with OSI discussions
Describe the bug
The current status defining the CloudState is not backed-up with any weel know metric.
Describe how to reproduce the bug
See: https://www.asam.net/static_downloads/modelDocumentation/content/CloudState.html
Describe the expected behavior
A clear definition of the CloudState in a well known metric.
Consensus of the discussion in OSI (Harmonisation subgroup - https://github.com/OpenSimulationInterface/open-simulation-interface/issues/544) is that it is probably the best way to go with the definition of the Deutscher Wetterdienst (https://www.dwd.de/DE/service/lexikon/Functions/glossar.html?lv2=100932&lv3=101016 and https://www.dwd.de/DE/wetter/thema_des_tages/2015/5/25.html) as this seems to be detailed enough for most use cases, is not too complex.
This proposes a scale from 0/8 to 8/8, which describes the total sky coverage in eighths.