Renaming variables and updating comments in get-param-value-from-key template to reflect generalized usage.
Adding parameterized handling via xref.elements.pagenum.in.class to add "pagenum" class values to XREFs to facilitate use of CSS Paged Media to add page numbers for paged outputs.
Merge pull request #141 from oreillymedia/pagenums

Parameterized handling for "pagenum" classes for print outputs