Introduce geolocation based definition of target region
The current approach on an index-based target region definition turns out to be inconvenient, especially when the target domain crosses the zero meridian. In light of this, we decided during the meeting on 16th March, to switch to a geolocation based definition of the target domain. The arguments will be the south-west corner and the number of grid points in longitude- and latitude direction (similar to our naming convention).