Step 1.
include "addAllRegionOptions.H"
Adds the -allRegions, -regions and -region options to argList.
Step 2.
include "getAllRegionOptions.H"
Processes the options with -allRegions selecting everything
from the regionProperties.
OR use -regions to specify multiple regions (from
regionProperties), and can also contain regular expressions
OR use the -region option
Specifying a single -regions NAME (not a regular expresssion)
is the same as -region NAME and doesn't use regionProperties
Creates a `wordList regionNames`
Step 3.
Do something with the region names.
Either directly, or quite commonly with the following
include "createNamedMeshes.H"
Creates a `PtrList<fvMesh> meshes`
STYLE: add description to some central include files
