Metadata download: Remove the option to lookup first edition dates as the service used to get the data no longer exists

See https://www.oclc.org/developer/news/2018/xid-decommission.en.html

src/calibre/ebooks/metadata/sources/identify.py

@@ -92,7 +92,9 @@ class ISBNMerge(object):
         self.isbnless_results = []
         self.results = []
         self.log = log
-        self.use_xisbn = True
+        # The xISBN service has been de-commissioned
+        # https://www.oclc.org/developer/news/2018/xid-decommission.en.html
+        self.use_xisbn = False
 
     def isbn_in_pool(self, isbn):
         if isbn:

src/calibre/ebooks/metadata/xisbn.py

@@ -31,6 +31,9 @@ class xISBN(object):
         return self.isbn_pat.sub('', isbn.upper())
 
     def fetch_data(self, isbn):
+        # xisbn service has been de-comissioned see
+        # https://www.oclc.org/developer/news/2018/xid-decommission.en.html
+        return []
         url = self.QUERY%isbn
         data = browser().open_novisit(url).read()
         data = json.loads(data)
@@ -104,5 +107,3 @@ if __name__ == '__main__':
     print pprint.pprint(xisbn.get_data(isbn))
     print
     print xisbn.get_associated_isbns(isbn)
-
-

src/calibre/gui2/preferences/metadata_sources.py

@@ -305,6 +305,7 @@ class ConfigWidget(ConfigWidgetBase, Ui_Form):
         r('swap_author_names', msprefs)
         r('fewer_tags', msprefs)
         r('find_first_edition_date', msprefs)
+        self.opt_find_first_edition_date.setVisible(False)
         r('append_comments', msprefs)
 
         self.configure_plugin_button.clicked.connect(self.configure_plugin)