[cleanup] Simplify list concatenating
[cleanup] Simplify list concatenating

- instead of having two different line formatting string depending on
  image or category namespaces let page.title() do the job
- do not collect article items if the list page already exists
  and could not be overwritten or appended
- make some variables pep8 compliant

Change-Id: I799d179bce6247a8067d7a39b4ed72598f6277a5

wikimedia/pywikibot-core,wikimedia/pywikibot-core