Marvel: Add indices.count in Cluster Stats

Closes elastic/elasticsearch#517

Original commit: elastic/x-pack-elasticsearch@6ecbf3d1ee

marvel/src/main/java/org/elasticsearch/marvel/agent/renderer/cluster/ClusterStatsRenderer.java

@@ -18,6 +18,7 @@ public class ClusterStatsRenderer extends AbstractRenderer<ClusterStatsMarvelDoc
 
     public static final String[] FILTERS = {
             "cluster_stats.nodes.count.total",
+            "cluster_stats.indices.count",
             "cluster_stats.indices.shards.total",
             "cluster_stats.indices.shards.index.replication.min",
             "cluster_stats.indices.docs.count",

marvel/src/test/resources/samples/marvel_cluster_stats.json

@@ -3,6 +3,7 @@
   "timestamp": "2015-07-22T15:54:02.979Z",
   "cluster_stats": {
     "indices": {
+      "count": 10,
       "shards": {
         "total": 1,
         "index": {