improved pagebreak error messages and fixed xmlns:nordic error

 * added validation for page numbers to opf-and-html schema, for cross-document pagebreak validation
 * updated pagebreak validation rules to contain more information useful for locating the error
 * epub3.validate now loads all html documents in spine order, rather than simply all HTML documents.
   * TODO: check if this has any consequence for validating the navigation document in case the navigation document is not in the spine
 * added xmlns:nordic and xmlns:epub to the `<html>` element in the single-HTML representation when converting from EPUB to HTML
Merge pull request #188 from nlbdev/pagebreak-errors-and-xmlnsnordic

improved pagebreak error messages and fixed xmlns:nordic error
allow content in titlepage, fixed usage of author and title

doctitle and docauthor was already created in DTBook based on the OPF metadata from EPUB. However, there were inconsistencies to this rule, which should now be fixed.

 * allow content in titlepage, fixes #191
   * titlepage is validated like any other frontmatter, except that its h1 needs to have epub:type="fulltitle" and class="title". The conversion logic does not need these attributes anymore, but it's required by the guidelines, and it makes for good semantic markup and easy css styling anyway. added these rules to check that markup is according to guidelines:
     * `[nordic263] the titlepage must have a headline (and the headline must have epub:type="fulltitle" and class="title")`
     * `[nordic264] the headline on the titlepage must have a epub:type with the value "fulltitle"`
     * `[nordic264] the headline on the titlepage must have a class with the value "title"`
 * allow the use of epub:type="fulltitle" anywhere in content
 * allow the use of epub:type="z3998:author" everywhere where the `<author>` element would be allowed in DTBook. These rules are removed:
   * `[tpb135b] z3998:author is only allowed either in the titlepage or inside a poem`
   * `[nordic262] Only <h1 epub:type="fulltitle" class="title"> and <p epub:type="z3998:author" class="docauthor"> are allowed on the titlepage.`
 * renamed tpb135a into nordic135 and updated it to work with the way poems are marked up in guidelines revision 2015-1

 * made sure jacketcopy and endnote is properly mapped to cover and rearnote even when not running in legacy mode
 * convert `<author>` inside `<level1 class="titlepage">` into `<p epub:type="z3998:author" class="docauthor">` (won't ever happen though; `<author>` is not allowed in this context)
 * convert `<h1>` inside `<level1 class="titlepage">` into `<h1 epub:type="fulltitle" class="title">`
 * added/updated XSLT unit tests for the changes

 * fixed mapping of poem title
 * fixed mapping of poem author
 * fixed mapping of poem
 * added/updated XSLT unit tests for the changes
Merge pull request #205 from nlbdev/content-in-titlepage-and-poem-title-author

allow content in titlepage, fixed usage of author and title
added test for prodnote mapping issue in cover

fixes #151 as of PR #205 (this commit adds tests)
simplified frontmatter/bodymatter/backmatter types in schema

 * added preface to frontmatter, fixes #189
 * added introduction to bodymatter, fixes #196
allow linegroups to be divs when they do not contain headlines
added error message for missing epub:type on footnotes/rearnotes ol

fixes #187
Report error if the navigation document occurs in the spine

fixes #201
require id on pagebreaks
Merge pull request #208 from nlbdev/issue-151-187-189-196

Several bugfixes and improvements to preface, introduction, footnotes, linegroups, pagebreak ids, validation
fix toc issues
Merge pull request #226 from nlbdev/fix-toc-issues

fix toc issues
don't require type on footnotes/rearnotes ol, allow rearnotes in backmatter

 * allow rearnotes in backmatter
 * add error messages which lists allowed types for cover, frontmatter, bodymatter and backmatter
 * removed requirement that the ol element wrapping footnotes and rearnotes must have the epub:type "footnotes" or "rearnotes"; fixes #214
don't use z3998:production in cover

fixes #220
Merge pull request #227 from nlbdev/dev-20141123

drop z3998:production from cover, rearnotes in backmatter, foot-/rearnotes not required on ol
added category 1-3 detection to epub validation
Merge pull request #228 from nlbdev/category-detection

added category 1-3 detection to epub validation
Removed nordic266a (ol in rearnotes) and updated message for nordic204c
support for the code element