Enables retrieving broken redirects from special page and try to fix them

There is a new behavior for broken redirects. They are no longer
just deleted but bot tries to fix broken redirects:

- Now we can read broken redirects from special page
- First check we can solve the problem. We look at the deleted
  target page and check whether that has been moved. If yes, we
  have found the new target and we repair the broken redirect with
  the already existing message 'redirect-fix-broken-moved'.
- Otherwise we delete the broken redirect if the new -delete option
  is given and the bot has sysop rights. Without sysop rights we
  place a speedy deletion template at the page if we have some.
- Documentation updated.

Change-Id: I5a0f50d4145f1510bd2a430d3f5db0dbb081ef7c