Updating GitLab project URL and copyright information

CMakeLists.txt

docker/dockerfile

license.txt

readme.md

src/developer_documentation.dox

src/main.cpp

src/main.hpp

src/marking.cpp

src/marking.hpp

src/markingscollection.cpp

src/markingscollection.hpp

src/mincoversetcomputer.cpp

src/mincoversetcomputer.hpp

src/node.cpp

src/node.hpp

src/orderedtuples.cpp

src/orderedtuples.hpp

src/petrinet.cpp

src/petrinet.hpp

src/pnmlreader.cpp