improvements to reflinks.py

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

- use core-like page.text when possible

- pep8-compliant comments

Change-Id: Idd851f6e1e2e6f81888854713324f602d44c0b54
Merge "improvements to reflinks.py"