Merge all changes from JOSS into master

.gitlab-ci.yml

.gitmodules

CMakeLists.txt

README.md

cmake/CoinUtils/coin_utils_configure.sh

cmake/coin-Clp/clp_configure.sh

docker/Dockerfile_ci

docker/Dockerfile_full_install

docs/cpp_api/Inputs_sec.rst

docs/cpp_api/cpp_api.rst

docs/python_api/py_Inputs.rst

docs/python_api/py_Inputs_sec.rst

docs/python_api/py_model.rst

docs/python_api/py_node.rst

docs/python_api/py_solvers.rst

docs/python_api/python_api.rst

docs/quick_start/Installation.md

docs/quick_start/code_ref.md

docs/tutorial/0_intro.md

docs/tutorial/1_command_line.md