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

added free flow + porous media flow coupling case from tutorial; The case should be at the state 'Task B: Include slip-condition'; Can we verify the case and split it into two parts?