add "Link" action to permissions table and to the Key 3

This is a follow up of the PR https://github.com/openmicroscopy/ome-documentation/pull/289, which was closed. Although the conflict was resolved there, its setting was not done well. 

My local branches have been reset, and new, clean branch created with the same commits.
Also, the comments of mark from the PR https://github.com/openmicroscopy/ome-documentation/pull/289 are fixed here.