Merge branch 'fhennig/cuda-invoke' into 'master'

.gitlab-ci.yml

docs/source/_util/sfg_monkeypatch.py

docs/source/api/composer.rst

docs/source/api/lang.rst

docs/source/usage/config_and_cli.md

docs/source/usage/how_to_composer.md

src/pystencilssfg/composer/__init__.py

src/pystencilssfg/composer/basic_composer.py

src/pystencilssfg/composer/composer.py

src/pystencilssfg/composer/gpu_composer.py

src/pystencilssfg/context.py

src/pystencilssfg/extensions/gpu.py

src/pystencilssfg/generator.py

src/pystencilssfg/ir/__init__.py

src/pystencilssfg/ir/call_tree.py

src/pystencilssfg/ir/postprocessing.py

src/pystencilssfg/lang/cpp/std_tuple.py

src/pystencilssfg/lang/expressions.py

src/pystencilssfg/lang/gpu.py

tests/extensions/test_gpu.py