Merge branch 'convdev-docs' into 'master'

Convdev docs

See merge request !12189

doc/user/admin_area/monitoring/convdev.md

+# Conversational Development Index
+
+> [Introduced][ce-30469] in GitLab 9.3.
+
+Conversational Development Index (ConvDev) gives you an overview of your entire
+instance's feature usage, from idea to production. It looks at your usage in the
+past 30 days, averaged over the number of active users in that time period. It also
+provides a lead score per feature, which is calculated based on GitLab's analysis
+of top performing instances, based on [usage ping data][ping] that GitLab has
+collected. Your score is compared to the lead score, expressed as a percentage.
+The overall index score is an average over all your feature scores.
+
+![ConvDev index](img/convdev_index.png)
+
+The page also provides helpful links to articles and GitLab docs, to help you
+improve your scores.
+
+Your GitLab instance's usage ping must be activated in order to use this feature.
+Usage ping data is aggregated on GitLab's servers for analysis. Your usage
+information is **not sent** to any other GitLab instances.
+
+If you have just started using GitLab, it may take a few weeks for data to be
+collected before this feature is available.
+
+This feature is accessible only to a system admin, at
+**Admin area > Monitoring > ConvDev Index**.
+
+[ce-30469]: https://gitlab.com/gitlab-org/gitlab-ce/issues/30469
+[ping]: ../settings/usage_statistics.md#usage-ping

doc/user/admin_area/settings/usage_statistics.md

@@ -3,7 +3,8 @@
 GitLab Inc. will periodically collect information about your instance in order
 to perform various actions.
 
-All statistics are opt-out, you can disable them from the admin panel.
+All statistics are opt-out, you can enable/disable them from the admin panel
+under **Admin area > Settings > Usage statistics**.
 
 ## Version check