Cli skeleton

This provides a skeleton of the CLI. It is creating a `ProjectData` object and that's all for now.
Next steps shall include setup of processes, calling global assembly, and solving the resulting system of linear equations.
If I remember this correctly it is because of the `GEOObjects` which becomes `GEOModels` if `OGS_BUILD_GUI` is defined. If no gui is build, Qt and VTK is not linked too.
I shall check this one more time.