Let tarch VTK plotters pass file creation errors to ExaHyPE plotters

This is something where I want to patch Peano and subsequently send the patch to Tobias:

Currently it's annoying that some ExaHyPE plotters stop the program when they cannot open output files (the ASCII/CSV writers as well as my CarpetHDF5 writer) while other silently ignore this issue (Tobias tarch-based VTK writers). Clearly, we want the user to be able to control whether problems at output shall be severe or not.

I can easily implement this in the ExaHyPE codebase, but I don't control peano, so I have to make sure Peano passes such errors into exahype's domain.

=> TODO @ Sven.