tests: updated tests after ebook_obj refactor
client: identifier metadata extract bug fix and test
client: don't calculate MD5 twice..
client: filename is not needed as part of EbookObject
client: smarter serialisation of EbookObjects from/to the cache
client: serialize EbookObjects just before sending to ogreserver
client: check for duplicate filehashes during search
client: don't report errors when only warnings occur
client: stats command
tests: prevent subprocess being mocked before calibre_ebook_meta_bin fixture