docs: what's new in v5.2 and docker installation updates

[skip ci]

docs/sources/guides/whats-new-in-v5-2.md

@@ -17,9 +17,11 @@ Grafana v5.2 brings new features, many enhancements and bug fixes. This article
 * [Elasticsearch alerting]({{< relref "#elasticsearch-alerting" >}}) it's finally here!
 * [Cross platform build support]({{< relref "#cross-platform-build-support" >}}) enables native builds of Grafana for many more platforms!
 * [Improved Docker image]({{< relref "#improved-docker-image" >}}) with support for docker secrets
+* [Security]({{< relref "#security" >}}) make your Grafana instance more secure
 * [Prometheus]({{< relref "#prometheus" >}}) with alignment enhancements
+* [InfluxDB]({{< relref "#influxdb" >}}) with support for a new function
 * [Alerting]({{< relref "#alerting" >}}) with alert notification channel type for Discord
-* [Dashboards & Panels]({{< relref "#dashboards-panels" >}})
+* [Dashboards & Panels]({{< relref "#dashboards-panels" >}}) with save & import enhancements
 
 ## Elasticsearch alerting
 
@@ -42,11 +44,24 @@ We've been longing for native ARM build support for a long time. With the help f
 The Grafana docker image now includes support for Docker secrets which enables you to supply Grafana with configuration through files. More
 information in the [Installing using Docker documentation](/installation/docker/#reading-secrets-from-files-support-for-docker-secrets).
 
+## Security
+
+{{< docs-imagebox img="/img/docs/v52/login_change_password.png" max-width="800px" class="docs-image--right" >}}
+
+Starting from Grafana v5.2, when you login with the administrator account using the default password you'll be presented with a form to change the password.
+By this we hope to encourage users to follow Grafana's best practices and change the default administrator password.
+
+<div class="clearfix"></div>
+
 ## Prometheus
 
 The Prometheus datasource now aligns the start/end of the query sent to Prometheus with the step, which ensures PromQL expressions with *rate*
 functions get consistent results, and thus avoid graphs jumping around on reload.
 
+## InfluxDB
+
+The InfluxDB datasource now includes support for the *mode* function which allows to return the most frequent value in a list of field values.
+
 ## Alerting
 
 By popular demand Grafana now includes support for an alert notification channel type for [Discord](https://discordapp.com/).
@@ -64,6 +79,20 @@ when you actually want to overwrite those settings.
 
 <div class="clearfix"></div>
 
+### Import dashboard enhancements
+
+{{< docs-imagebox img="/img/docs/v52/dashboard_import.png" max-width="800px" class="docs-image--right" >}}
+
+Grafana v5.2 adds support for specifying an existing folder or create a new one when importing a dashboard, a long awaited feature since
+Grafana v5.0 introduced support for dashboard folders and permissions. The import dashboard page have also got some general improvements
+and should now make it more clear if a possible import will overwrite an existing dashboard, or not.
+
+This release also adds some improvements for those users only having editor or admin permissions in certain folders. Now the links to
+*Create Dashboard* and *Import Dashboard* is available in side navigation, dashboard search and manage dashboards/folder page for a
+user that has editor role in an organization or edit permission in at least one folder.
+
+<div class="clearfix"></div>
+
 ## Changelog
 
 Checkout the [CHANGELOG.md](https://github.com/grafana/grafana/blob/master/CHANGELOG.md) file for a complete list