Use f90nml to change namelists instead of sed/regex

[kinow]

• https://pypi.org/project/f90nml/
• https://github.com/marshallward/f90nml

[kinow]

I am still using sed because this way I can run the workflow without having to install Python/f90nml/etc, and it should work on Autosubmit or ecFlow.

I will actually raise an issue in mHM to ask if it'd be possible to have a command line flag for the configuration, e.g.

mhm -config eval_Per(1)%yStart=blabla -config eval_Per(1)%dEnd=30 ... and so mhm called f90nml and modified the value. This way this solution would work with AS / ecFlow /etc, without having to install anything on the workflow nodes.