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.
IMO this is specific to some approaches and should be moved to somewhere else, if this class is inteded to be used as general BC data. We don't search mesh nodes for Neumann conditions and even for Dirichlet condition if penalty or Lagrangian multiplier are used.