Adding support for "pagenum" style functionality

This PR adds two new params and corresponding handling to support specifying a "pagenum style" for internal cross-references for paged (PDF) outputs. If the `autogen.xref.pagenum.style` param is enabled, then the toolchain will decorate `<a>` elements representing cross-references in body text and autogenerated index with a `data-xref-pagenum-style` attribute based on list-style-type enumerations (decimal, decimal-leading-zero, lower-roman, upper-roman, georgian, armenian) in `xref.pagenum.style.for.section.by.data-type`, e.g:

````xml
<xsl:param name="xref.pagenum.style.for.section.by.data-type">
acknowledgments:decimal
afterword:decimal
appendix:decimal
bibliography:decimal
chapter:decimal
colophon:decimal
conclusion:decimal
copyright-page:decimal
dedication:lower-roman
foreword:lower-roman
glossary:decimal
halftitlepage:lower-roman
index:decimal
introduction:decimal
preface:lower-roman
titlepage:lower-roman
toc:lower-roman
</xsl:param>
````

These `data-xref-pagenum-style` attributes can then be used in Paged Media CSS to set numeration styles for cross-reference page references.