tests working for Pipeline 2 v1.8

 * allow epub:type="toc" in nav doc
 * use px:epub3-store
 * removed step/fileset-store.xpl and step/fileset-move.xpl (they are bundled with v1.8)
 * adding original-base to dtbook fileset when loading dtbook
 * removed fileset.in port when invoking px:html-to-fileset - (this should be added back in a later release of Pipeline!)
   * as a temporary workaround in html-to-epub3.convert.xpl, the original-href is fixed manually
 * swapped order of viewport and dc:identifier in html head
 * changed type of pagenum with id="page_4" from "normal" to "front"
 * added original-href attribute to test fileset in html-to-epub3.convert.xprocspec
 * added classes "num-with-space" and "num-word" to test documents
 * updated .gitignore according to restructured folder structure