BUG: simpleFoam: moved createFvOptions.H into createFields.H for -postProcess option

To unsure fvOptions are instantiated for post-processing createFvOptions.H must
be included in createFields.H rather than in the solver directly.

Resolves bug-report https://bugs.openfoam.org/view.php?id=2733

BUG: porousSimpleFoam: moved createFvOptions.H into createFields.H for -postProcess option

Resolves bug-report https://bugs.openfoam.org/view.php?id=2733

BUG: solvers: Moved fvOption construction into createFields.H for post-processing

This ensures that the fvOptions are constructed for the -postProcessing option
so that functionObjects which process fvOption data operate correctly in this
mode.