Resolve "Add support for using of the OSKAR beam model in wsclean"

cpp/CMakeLists.txt

cpp/griddedresponse/CMakeLists.txt

cpp/griddedresponse/griddedresponse.h

cpp/griddedresponse/lofargrid.h

cpp/griddedresponse/oskargrid.cc

cpp/griddedresponse/oskargrid.h

cpp/oskar/oskarelementresponse.cc

cpp/telescope/oskar.cc

cpp/telescope/oskar.h

demo/CMakeLists.txt

demo/comparison-oskar/CMakeLists.txt

demo/comparison-oskar/compare_stationresponse.py

demo/comparison-oskar/run_oskar_simulation.py

demo/comparison-oskar/skalowmini-coef.tm/layout_ecef.txt

demo/wsclean-oskar/CMakeLists.txt

demo/wsclean-oskar/aterm.conf

demo/wsclean-oskar/make_model_images.py

demo/wsclean-oskar/make_model_images.sh

demo/wsclean-oskar/run_oskar_simulation.py

demo/wsclean-oskar/run_oskar_simulation.sh