Implement VTK libraries for XDMF output.
Debug IO using VTK libraries on Win64.
Fix errors reported by valgrind.
Comment-out resolution-reset line.
Make edits related to VTK IO and MSVC heap usage.
Commit changes prior to merge.
Merge remote-tracking branch 'origin/master'
Debug VTK IO.
Debug VTK IO.
Debug VTK IO.
Remove unneeded line.
Update VTK IO.
Set relative name for heavy data.
Remove manual setting of XDMF heavy data name.

Heavy data file written to working directory of application, which is
not (in general) the desired output directory.  I think editing the XML
file for an updated path is easier than having to remember to copy/move
the actual data file.
Minor changes.
Fix heavy data name.
Improve documentation and file IO.

Update documentation for class.  Add command to remove existing XDMF/HDF5 file prior to writing data.  Since HDF5 can contain multiple arrays this is to avoid potential conflicts if a file of the desired name already exists.  Current usage is compatible with overwriting the existing file.
Remove forcing of data-copy on windows.
Add code to force '/' rather than '\' in Windows XDMF output file names.
Add elapsed-time member.