compares two VTU files and computes the errors. The code is written in C++ and need two vtu files as input. The code is a mess, but it does what it should. VTK libraries are needed as a dependency

added darcy solver now

This case still needs preCICE

Merge branch 'feature/ff-pm-coupling' of https://git.iws.uni-stuttgart.de/dumux-appl/dumux-precice into feature/ff-pm-coupling

This only works with a special feature branch in which the iterative coupling does not work

Updated code to current version on my laptop. Need to cleanup up code. It has a lot of debugging output.

Good news: Partitioned results no looke very similar to monolithic result after Kilian has changed the boundary conditions in the monolithic case

Added functions to write pressure and velocity from solvers directly to csv

Added functions to write pressure and velocity from solvers directly to csv

Change coupling to:
pm receives pressure and communicates velocity

WIP

- Write routines to extrapolate pressure.
- Solvers use data from preCICE now
- Some hacks to make it work for now

- main_ff and main_pm will update preciceDataIDs of the problem after quantities are announced.
- PreciceAdapter uses its own indexing (always starting at zero) instead of preCICE indexing. This allows for easier data access
- member `dataVectors_` is increased in size as soon as a new quantity is added to the adapter

[ff-pm] mild integration of precice for ff-pm testcase; Need to integrate/reconstruct boundary values properly