This commit adds an option to build using CMake by adding
CMakeLists.txt. CMake builds are consistent with the builds currently
produced.

For Linux build, CPack produces artifacts consistent with the current
RPM specification.

CMake is also added to the CI pipeline in main.yml.

* cli/gcdmodel.cpp: Fix typos in comments.

* cli/gcdmodel.cpp (CGcdData::fixModelAndSubmodelOrder): Fix typos in comments.

* cli: Support "max" as an alias to the maximum value for the order switch.

* cli/cmdline.cpp (parseArg): Understand "all" for the order switch.
(showUsage): Document it.
* cli/gcdmodel.cpp (CGcdData::fixModelAndSubmodelOrder): Ensure the
root model order gets recomputed when "/o:max" was provided as argument.
* cli/model.h (UNDEFINED_ORDER): Redefine as the minimum int value.
(MAXIMUM_ORDER): New constant.
* doc/pict.md: Document it.
* test/arg/.tests: Add test.

Co-authored-by: Maxim Cournoyer <maxim.cournoyer@savoirfairelinux.com>