Review Pipeline: Notification when anno wasn't saved

[Daniel595]

Is your feature request related to a problem? Please describe.
When reviewing an anno-task it often happens to me, that I forget to save the applied changes. When changing to the next image it might happen that you don't even recognize that you just deleted your changes.

Describe the solution you'd like
When changes were made and not saved and next image is requested -> popup with buttons discard and save