EPUB toc.ncx and content.opf must agree about book ID

[thsutton]

Section 2.4.2 of the OPF specifications mentions that the NCX file is required to have a <meta name="dtb:id"> with a "reference to the OPF unique ID".

Wikipedia suggests that this element "should match [its] analog in the OPF file" and the IDPF's epubcheck agrees that the dc:identifier and dtb:uid values must agree.

pandoc 1.12.1 uses the supplied dc:identifier value but continues to use the generated UUID in the NCX.