Add support for Grafana

This patch enables support for Grafana and provides a new dashboard.

galera/meta/grafana.yml

@@ -0,0 +1,3 @@
+dashboard:
+  galera:
+    template: galera/files/MySQL.json

metadata/service/support.yml

@@ -11,3 +11,5 @@ parameters:
         enabled: true
       config:
         enabled: true
+      grafana:
+        enabled: true