A correct MPI program should do that.
As MPI_Finalize is part of the destructor of MainObject we need to
make sure that it's destructor is called before the return statement.
We do that manually by resetting the unique_ptr that we now use to
store the MainObject,
this is used transferring ownership of setup structures to the
simulator. drop all the flowEbosXXX set deck methods and use the
generic vanguard. also means various structs that were only passed
in the blackoil simulator are now passed in all simulators.
Initialization is now done in the Main::initMPI() method.
For configurations with dune-fem, this also caused crashes
with dune-fem versions prior to 2.8.
this is very convenient during development.
we can then remove the FLOW_BLACKOIL_ONLY option,
as it is no longer needed - use the flow_blackoil binary instead.
however we need to keep this support in Main.hpp due to the python
bindings relying on it.
