EPUB Input: Handle EPUB files with incorrect media types for the spine items when converting. Fixes #1273471 [OEBError: Spine is empty](https://bugs.launchpad.net/calibre/+bug/1273471)
EPUB Output: Fix splitting of HTML files not updating links in the <pageList> section of the NCX file
Edit Book: Enable editing of page map XML files
Edit Book: Add check for spine items with incorrect media-type specified in the manifest