Add documentation. (#321)

Add documentation that covers:

- Prediction
- Measuremnt
- REST API

Add Python scripts that support automatic documentation generation using the Sphinx
sphinxcontrib.eval extension.

Add automatic update/ test for REST API documentation.

Filter proxy endpoints from REST API documentation.

Signed-off-by: Bobby Noelte <b0661n0e17e@gmail.com>

src/akkudoktoreos/prediction/weatherabc.py

@@ -56,7 +56,7 @@ class WeatherDataRecord(PredictionRecord):
         default=None, description="Low Clouds (% Sky Obscured)"
     )
     weather_medium_clouds: Optional[float] = Field(
-        None, description="Medium Clouds (% Sky Obscured)"
+        default=None, description="Medium Clouds (% Sky Obscured)"
     )
     weather_high_clouds: Optional[float] = Field(
         default=None, description="High Clouds (% Sky Obscured)"