Improve initialization of weather based agents

[t-ober]

When initializing pv agents we look for the nearest weather coordinates within WeatherSource.getNearestCoordinatesWithDistances. This method calculates the distance to every known coordinate, sorts them and returns the 4 nearest ones. This is painfully slow since for every agent we calculate the distance to 700.000 coordinates and sort them.

Improvement ideas:

1. Shrink down the coordinate source for the simulation run to the area that is actually significant
2. Find an algorithm that can search for the nearest coordinates much more efficiently
3. Do both