Code Review thread

As a User I'd like to have a button to continue a discussion of a single code-line so that I know exactly that my comment will be displayed below

Acceptance Criteria:

• All comments to the same line should be wrapped by some area (see attachment)
• Add Comment button (or link) should appear at the bottom of the area.
• Only users who have permissions to comment should see Add Comment button.
• After pressing the button, the same text input should appear as during the first comment adding (or comment editing)

i18n criteria:

• Add Comment -> Добавить Комментарий -> Додати коментар

See in attachments how this is implemented on GitHub, we should take similar approach.