Merge pull request #45 from oreillymedia/xmlschema

Adding cover spec to HTMLBook schema
Base starting point for indexgen stylesheet: "basic" index generation logic from xhtml/autoidx.xsl in docbook-xsl project.
Adding params and proper xsl:stylesheet and xsl:output declarations.
Necessary id decoration for TOC/index autogeneration. Also moved default rule to common.xsl
New master htmlbook.xsl stylesheet.
Start of work to adapt indexgen for HTMLBook
Remove extraneous imports of common.xsl
More work on adapting indexgen, and pulled in overrides for "reference" mode of "indexterm" template.
Continuing adapting indexgen for HTMLBook.
Finished first pass at adapting indexgen.xsl for HTMLBook.
Pulling in localizations for different languages from docbook-xsl for use in htmlbook-xsl
Added get-localizations template. Fixed bugs in htmlbook.xsl localization logic.
Bug fixes in indexgen.xsl, and set up gentext logic for "Symbols" header.
Refactoring to put all params in a separate stylesheet file (param.xsl).
Refactoring :)
Error checking for Index autogeneration.
Refactoring.
Fixed bugs in get-localization-value template.
Added template for triggering index generation.
Bug fixes for many missed mappings from DB to HTMLB.