standardize isbn.py

- remove duplicate IsbnBot class

- IsbnBot extends pywikibot.Bot and uses self.userPut()
  with built-in 'always' option

- remove the pageTitle mechanism
  per I3d0c64bd0f4aac2a2c3cf375d84e77cb364868ad
  and Ic5983b64cbc0cd96c98c105574ccb1db6dbaf9a6

- let the standard GeneratorFactory parse the '-namespace:' argument

- optimize the argument parsing for '-always', '-to13' and '-format'

- catch pywikibot.LockedPage only in the block that
  actually tries to update the page

- remove obsolete script name from pywikibot.showHelp()

Change-Id: I4843c296a9a894cce23ce3881ccd7683ba2fe302
Merge "standardize isbn.py"