TMSS-272: merged master into this feature branch

Docker/lofar-ci/Dockerfile_ci_sas

...ceAssignment/ResourceAssigner/test/ra_test_environment.py

SAS/Scheduler/src/CMakeLists.txt.build_without_lofar_cmake

SAS/Scheduler/src/schedulergui.cpp

SAS/TMSS/src/remakemigrations.py

SAS/TMSS/src/tmss/settings.py

SAS/TMSS/src/tmss/tmssapp/migrations/0001_initial.py

SAS/TMSS/src/tmss/tmssapp/migrations/0002_populate.py

SAS/TMSS/src/tmss/tmssapp/models/specification.py

SAS/TMSS/src/tmss/tmssapp/populate.py

SAS/TMSS/src/tmss/tmssapp/serializers/specification.py

SAS/TMSS/src/tmss/tmssapp/subtasks.py

SAS/TMSS/src/tmss/tmssapp/viewsets/specification.py

SAS/TMSS/src/tmss/urls.py

SAS/TMSS/test/t_tmss_test_database.py

SAS/TMSS/test/t_tmssapp_specification_REST_API.py

SAS/TMSS/test/test_utils.py

SAS/TMSS/test/tmss_test_data_django_models.py

SAS/TMSS/test/tmss_test_data_rest.py