Use an html5 standard header, eliminate xhtml refs
Use an html5 standard header, eliminate xhtml refs

The document started life a long time ago as an xhtml document. At this
point we're only targetting modern browsers anyways, make it explitly be
a modern html5 implementation.

re #842 (0.25)

victor-lin/npact,victor-lin/npact,victor-lin/npact,victor-lin/npact,victor-lin/npact,NProfileAnalysisComputationalTool/npact,NProfileAnalysisComputationalTool/npact,NProfileAnalysisComputationalTool/npact,NProfileAnalysisComputationalTool/npact,NProfileAnalysisComputationalTool/npact