Revert "Delete default_flux.json"
Revert "Delete default_flux.json"

This reverts commit df60f2a454dabc01e62c99bc4be96ae1c092d846.

mwiesenberger/feltor,feltor-dev/feltor,feltor-dev/feltor,mwiesenberger/feltor,feltor-dev/feltor,mwiesenberger/feltor,feltor-dev/feltor,mwiesenberger/feltor