Fix contrib/man/md/docker-import.1.md warning ("macro `tar.gz,' not defined")

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Revised and fixed links on dockerrepo.md

Docker-DCO-1.1-Signed-off-by: Fred Lifton <fred.lifton@docker.com> (github: fredlf)
Fixed a typo

Docker-DCO-1.1-Signed-off-by: Fred Lifton <fred.lifton@docker.com> (github: fredlf)
Remove mention of SSH passphrase, it was only present in v0.12

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@docker.com> (github: SvenDowideit)
Merge pull request #6605 from SvenDowideit/6423-remove-b2d-ssh-passphrase-prompt

Remove mention of SSH passphrase, it was only present in v0.12
Merge pull request #6426 from tianon/fix-import-man-error

Fix contrib/man/md/docker-import.1.md warning ("macro `tar.gz,' not defined")
Merge pull request #6581 from fredlf/copyedit_dockerrepo

Revised and fixed links on dockerrepo.md