L2SS-445: Forward logs from the Docker containers to ELK

Closes L2SS-445

docker-compose/elk/logstash/conf.d/20-parse-grafana.conf

+filter {
+  if [program] == "grafana" {
+    kv { }
+    mutate {
+      rename => {
+        "t" => "timestamp"
+        "lvl" => "level"
+        "msg" => "message"
+      }
+      uppercase => [ "level" ]
+    }
+    date {
+      match => [ "timestamp", "ISO8601" ]
+    }
+  }
+}