"mapCenter" property of config file in WGS84

[JakobMiksch]

currently the mapCenter property in the config file needs to be provided in the map projection, however often coordinates are not really intuitive e.g. "mapCenter": [930473.6,6348916.5].

It might be useful to have a separet property where the center can be provided in latitude/longitude. Maybe something like
``"mapCenter": [49.1, 8.2]`

OpenLayers 7 might also switch to use WGS84 coordinates as default CRS for the API. Hence, Wegue would be consistent with than.