- These classes were imported (copied) from the dune-porsol repository,
and copies remain there for the time being.
- Some of the black oil fluid classes that are in opm-core, such as the
SinglePvt* classes, are direct descendants of the Miscibility* classes
that have been removed.
- At some point, we may modify dune-porsol to use the new fluid interfaces
from opm-core, but for now we keep using the existing code as-is.