[GEOS-6564] unit test to expose issue with WCS, mosaic and multi dimensional output

This unit test mimicks my local WCS setup. It may be a little bit too complex for what I want to illustrate, but I hope that I can expand it in the future to test other use cases based on this setup. The included test data is based on a dummy data set which I created for an other unit test in the netcdf image format module.