Ignore nested lists following scalar data in openFOAM lists.
vtkOpenFOAMReader would fail to read files if a list of the form:
(scalar (scalar scalar) )
was found, as it only supported nested lists to appear before all 'loose' scalars. This patch allows such files to be read by discarding the nested list data and printing a warning, instead of failing to finish reading the file.
This is to work around an issue reported on the mailing list where such a list was used in a field that was not needed for visualization.