use insite parameter of Page.title() to format links on target page

Changing the config settings is no longer needed to get sensible
backlinks. This is follow up for https://gerrit.wikimedia.org/r/#/c/105436/

Additional changes:
- rewrite the documentation tho the common format
- remove the unused -fromfamily -fromlang comments. We may just use
  -lang and -family option for the source site
- use the current site paramteters as default for the target site
  but raise an exception if both are equal. This means you may
  ommit eigther -tolang or -tofamily option.
- DuplicateFilterGenerator is always the last generator we see
  for gen. Thus we do not display the generator but the arguments.

Change-Id: I5d4cd6673140ad87f26e884007ffb6d3434ecc56
Merge "use insite parameter of Page.title() to format links on target page"