Add setting for minimal degrees search distance for weather station

[nhoening]

We use the variable max_degree_difference_for_nearest_weather_sensor with a default value of 2, when looking up weather sensors. So both latitude and longitude must be within this margin of error.

• Isn't 2 on the high side?
• It should become a setting which can be overwritten in flexmeasures.cfg. We can easily add this in __init__.py

[Ahmad-Wahid]

Do we consider the best canditate between these 2 stations based on the shortest distance from the location?

[nhoening]

The candidates are ordered by distance and the nearest is chosen