[IMPR] imprvements for create_isbn_edition.py

• capitalize constants
• shorten is_in_list function
• repo and wikidata_site is the same object, drop one of them
• remove logger and use pywikibot.logger functions instead
• use enumerate to count loops
• fix some globals
• use return in main() instead of sys.exit()
• use bare return statements in amend_isbn_edition because return result is not used

Change-Id: I7415d910bda1fb384b4076df09f899c24e270b56