Make OpenMC and NetCDF Conditional Dependency

[Fuad-HH]

OpenMC is needed when we want OpenMC output, and NetCDF is needed for Degas2. Make them conditional so that if the user wants only one of them, it will be easier to install. Depending on this, only the necessary CLIs have to be installed.

[Fuad-HH]

Did not find any graceful way to separate them… We need conditional installation of the CLI tools based on the installation conditions.