Make all flux variables default constructable.
This merge request contains backward imcompatible. All flux variables now have to be default constructed. Implementers of flux variables need to make their implementation default construcable too. All calls to the old non-default ctors will throw errors at runtime and emit deprecation warning at compile time. FluxVars are no constructed and update like this:
FluxVariables fluxVars; fluxVars.update(...)
Being default contructable offers more flexible class inheritance and more flexible caching possiblities.
- Simplifiy 2pnc and 2pncmin flux variables through inheritance
- Deprecates the unused
rhoFactor_in 2p2c, 2pnc, and 3p3c
Fix 2pncmin test