WIP Fix replies toggle visual glitch in edit mode

This fixes an issue (#1808) where the replies button overlaps the license message when the editor is switched into edit mode. 

This is achieved by only applying the negative margin on the `thread-reply` element when the annotation is in "view" mode.

An `on-mode-change` handler is now passed to the annotation directive via an attribute which is called when the view mode changes. A class applying the negative margin is then toggled on the reply element in the thread template.
Thanks for the hint, I'd tried that actually, and it still didn't work. It turns out that `this` when called by the annotation controller is actually the annotation scope. So I was setting `inEditMode` on the wrong object. Using a double arrow here fixes the issue.

I haven't looked into why it's called in the annotation scope, I guest something to do with the way the attribute is passed. Frustrating either way.