Add documentation for the "Only allow merge requests to be merged if all...

Add documentation for the "Only allow merge requests to be merged if all discussions are resolved" feature
Signed-off-by: Rémy Coutable <remy@rymai.me>

doc/user/project/merge_requests/merge_request_discussion_resolution.md

@@ -33,7 +33,25 @@ resolved discussions tracker.
 
 !["3/4 discussions resolved"][discussions-resolved]
 
+## Only allow merge requests to be merged if all discussions are resolved
+
+> [Introduced][ce-7125] in GitLab 8.14.
+
+You can prevent merge requests from being merged until all discussions are resolved.
+
+Navigate to your project's settings page, select the
+**Only allow merge requests to be merged if all discussions are resolved** check
+box and hit **Save** for the changes to take effect.
+
+![Only allow merge if all the discussions are resolved settings](img/only_allow_merge_if_all_discussions_are_resolved.png)
+
+From now on, you will not be able to merge from the UI until all discussions
+are resolved.
+
+![Only allow merge if all the discussions are resolved message](img/only_allow_merge_if_all_discussions_are_resolved_msg.png)
+
 [ce-5022]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5022
+[ce-7125]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7125
 [resolve-discussion-button]: img/resolve_discussion_button.png
 [resolve-comment-button]: img/resolve_comment_button.png
 [discussion-view]: img/discussion_view.png

doc/user/project/merge_requests/merge_when_build_succeeds.md

@@ -40,7 +40,7 @@ hit **Save** for the changes to take effect.
 
 ![Only allow merge if build succeeds settings](img/merge_when_build_succeeds_only_if_succeeds_settings.png)
 
-From now on, every time the pipelinefails you will not be able to merge the
+From now on, every time the pipeline fails you will not be able to merge the
 merge request from the UI, until you make all relevant builds pass.
 
-![Only allow merge if build succeeds msg](img/merge_when_build_succeeds_only_if_succeeds_msg.png)
+![Only allow merge if build succeeds message](img/merge_when_build_succeeds_only_if_succeeds_msg.png)