Merge pull request #946 in CATS/clowder from feature/SEAD-984-previews-permissions to develop
* commit 'e27c0536babd168bead35bc5eac38d9034ebea7d':
Updating comments permissions on Private Mode (when logged in) Hiding the links on the Metadata view if the user is logged out.
Updating permissions for comments, sections and previews. Not showing the 'add metadata' section when the user is not defined. In the dataset page, when you are the owner updating the default option.