Fix the media-type of the navigation document. Now it will be possible for the pipeline to add the nav doc to the OPF's spine
Merge pull request #47 from daisy/nav-media-type

Fix the media-type of the navigation document.
zedai-to-epub3: Use the computed nav doc explicitly

Use the px:create-package-doc "nav-uri" option to force the nav doc
to declare in the the OPF to be the computed nav doc.
This prevents some conflicts if the HTML contains multiple toc navs.

Fixes daisy/pipeline-issues#416
Merge pull request #46 from daisy/issue/416

Closes #46
Port the DAISY 2.02 validator from Pipeline 1

Validations made in the DAISY 2.02 Validator Pipeline 2 script:

 * check that all references in and across documents are valid
 * check that only these kinds of files are present:
   application/xhtml+xml, text/html, application/smil+xml, audio/mpeg,
   audio/wav, image/jpeg, image/gif, image/png or text/css
 * check that SMIL-files conform to d202smil.rng (or d202msmil.rng for
   master.smil)
 * check that the NCC conforms to d202ncc.rng
 * check that the heading hierarchy in the NCC and content files are
   correct (no levels are skipped)
 * NOT IMPLEMENTED: inform whether MP3 files has ID3v2, and warn if
   the file is mono (single channel) or uses variable bit rate (VBR)
 * NOT IMPLEMENTED: compare audio duration with info from SMIL files
   and NCC totalTime (this was not implemented in DP1 either it seems?)
 * inform if SMIL audio clips are missing clip-begin or clip-end
   attributes
 * check that the SMIL metadata "ncc:totalElapsedTime" and
   "ncc:timeInThisSmil" values add up correctly, with a
   `timeToleranceMs` margin for error
 * check that the SMIL time values add up correctly to the NCC metadata
  "ncc:totalTime", with a `timeToleranceMs` margin for error
Fixes for inline comments