[IMPR] Write ignoring pages as a whole
[IMPR] Write ignoring pages as a whole

- PrimaryIgnoreManager.ignore accepts iterables
  and writes all it's content to the file
- a new attribute DisambiguationRobot.ignores holds all pages to be ignored
- use teardown() to call PrimaryIgnoreManager.ignore and write
  ignoring list finally

Change-Id: Idc4b0e541ed09f98352f217d913d734c641d7692

wikimedia/pywikibot-core,wikimedia/pywikibot-core