Merge pull request #1 from atomotic/master

failed indexing of invalid epub files
Bugfix in DB update, narrowed Exception, new TOC format from NCX, linear fragment progression.
Bugfix in DB update, narrowed Exception, new TOC format from NCX, linear fragment progression.
Added raw ODPS root catalogue generation via /opds-catalog
Fixed an error when a epub file has more than one <identifier> element, now parses the unique-identifier (thanks @atomotic).
dc:date could be not present in eub