Initial commit for view-links-refactor branch.

The motivation behind these changes is the ability to add edit links
that are nested lists.  This allows us to add another dropdown to the
edit bar, from kotti.multilingual.

action_links has disappeared from type_info.  Needs b/w compatiblity.
Also, a usage example.
Work around an issue with our event subscriber, which has problems cleaning things up.
Merge branch 'master' into view-links-refactor
I no longer remember why we needed to take care of double event registrations.

But I'm sure it'll pop up soon.  Which is when we'll need to write a test
.
Properly deprecate what was moved from 'kotti.views.util' to 'kotti.util'.
Try to make 'TypeInfo.action_links' a little backward compatible.
Another BBB fix; this time for '(View)Link.path'
Update CHANGES.txt with details for Link/ViewLink changes.
Fix deprecation warning.
Merge pull request #284 from Kotti/view-links-refactor

Rework implem of 'kotti.util.Link' ('ViewLink') to be more flexible.