"All Drafts" mode: all comments are drafts before completing review.

[klikh]

This mode can be useful for the following use case:
I review some large commit, and once I see something not clear or suspicious, I make a comment. However, since I haven't inspected the whole commit yet, I just can not get the logic because I don't see the whole picture yet. After I see all changed code, I understand, that the code is correct, and my comment becomes obsolete.

However, the author has already received a notification about my comment. He might have already spent time to answer the comment providing the information which I could recover myself.

Therefore it would be useful to mark all comments as drafts by defalt, and propose to "commit" them when user clicks "Complete".

[klikh]

Since #51 is implemented, there is no more need in any special mode for drafts: just write comments, but close popups via Esc, and they all will be saved as drafts.
To implement this feature we just need to propose to publish all drafts when "Complete review" button is clicked.