Split the adapter config file to one file per participant

For the OpenFOAM adapter we decided to have one adapter configuration file per participant, as shown here. This was done so that we don't need to modify the solver to accept an extra command-line argument (we want to keep the solvers intact).

If there is no problem with the current setup, I propose that we also change the CalculiX adapter to look for one YAML file per participant, instead of accessing a common file for all the participants. We already discussed this with @uekerman.

(as the links may break in the future, they refer to the precice-adapter-config.yml and config.yml of the heat exchanger tutorial for OpenFOAM and CalculiX)