EPUB, EPUB3 templates: Handle structured metadata on titlepage.

Previously we just expected 'title', 'subtitle', 'author', 'date'.
Now we still support those, but also support the format recommended
for epub metadata in the pandoc README:

    ---
    title:
    - type: main
      text: My Book
    - type: subtitle
      text: An investigation of metadata
    creator:
    - role: author
      text: John Smith
    - role: editor
      text: Sarah Jones
    identifier:
    - scheme: DOI
      text: doi:10.234234.234/33
    publisher:  My Press
    rights:  (c) 2007 John Smith, CC BY-NC
    ...
This commit is contained in:
John MacFarlane 2014-08-31 12:01:55 -07:00
parent b9d524c703
commit d1948ce012

@ -1 +1 @@
Subproject commit 7be841cee65db23378e659f3be443effa15168a3
Subproject commit 2d5491bc0b167a5b20c03e4bc02ef8b5fc20379f