13 add cppfmu as submodule

[StephanieKemna]

Resolves task 1 and 2 of #13

• Adding cppfmu as a submodule instead of adding the checked out files.
• Edited README with instructions for getting submodule
• Update CMAKE version to get rid of warning, and remove warnings-as-errors flags

[KristofferSkare]

Looks good!

However I am not able to test it easily because of the versioning problems in conan.

If everything still works as normal then it is probably done.

[KristofferSkare]

When pulling cppfmu as submodule I get Pylance errors in the conanfile.py. These errors are mainly that it disagrees with the typing of variables with the functions they are used in.

I am using python 3.12.

Does these errors appear for other python verisons?
And does the tool still work correctly? I do not have the new verison of onnxruntime to test it.

[StephanieKemna]

I tested with our hosted version of conan and then it all worked (though it still has the python recursive error), so I created this PR - so I assume it is all ok. But we can also leave this PR open until the conan thing is fixed for all.

I am unsure w.r.t. the pylance errors, did it not show those before? I was gonna check wrt python rmtree errors in other branch, will check there.

[StephanieKemna]

Hmm, it seems that there was no conanfile.py amongst the files from cppfmu that were in the repo. So I reckon that it is irrelevant then.

[StephanieKemna]

Verified again that it works here, merging branch, and we can create new issues if needed.