functionObjects only get detroyed when the runTime gets destroyed. So the
mesh is already destroyed and we cannot hold e.g. a volScalarField since
that will try to 'checkOut' from the objectRegistry(=mesh) upon destruction.
Note that we only see this in chtMultiRegionFoam.
end of Time::operator++. This allows to know if the next timeIndex will be
a dumping time. The function object "partialWrite" modifyes the write option
of the those fields which will be written down at given intervals of the overall
outout times.
