New annex.hardlink setting. Closes: #758593

* New annex.hardlink setting. Closes: #758593
* init: Automatically detect when a repository was cloned with --shared,
  and set annex.hardlink=true, as well as marking the repository as
  untrusted.

Had to reorganize Logs.Trust a bit to avoid a cycle between it and
Annex.Init.
Merge branch 'master' of ssh://git-annex.branchable.com