Fix reader to properly add content for DataStructure deprecated items.
Move whitespace trimming to reader where it is more convenient since
it can replace a check for the content being all whitespace.

AttributeType (Scalar). Also enable parsing of deprecated DataStructure
tag, synonym of DataItem.

Previously, when converting from xdmf to exodus, spatial partitioning (metis)
in xdmf was written as element blocks in exodus. However, exodus uses element
blocks to specify different materials and not as spatial partitioning for
parallel execution. We now write materials to blocks in exodus, indicated by
Block node sets in xdmf. This now makes the conversion of xdmf -> exodus the
exact inverse of the exodus -> xdmf function.

When converting exodus files to xdmf, element block information is written
to xdmf sets. When converting back to exodus, this information was
previously ignored. Now, we check whether we have block information written
as an xdmf set and use it to reproduce element blocks in exodus during
conversion.

Fix XdmfTopologyType vector to be reference rather than copy.

Heavy data files that are specified with relative paths should be
located with respect to the XML file location.

Fix compiler error on intel with XdmfExodusWriter missing include.

Heavy data files that are specified with relative paths should be
located with respect to the XML file location.

Fix compiler error on intel with XdmfExodusWriter missing include.

Added missing definition for macro SWIGPY_SLICE_ARG