Amazon metadata download: Fix parsing of some dates on amazon.de

Fixes #1238125 [Download Covers: Error parsing publish date for url](https://bugs.launchpad.net/calibre/+bug/1238125)
EPUB Metadata: Implement updating identifiers

EPUB Metadata: Implementing updating identifiers in the epub file from
calibre when polishing or exporting the epub

ebook-meta: Add an --identifier option to set identifiers.