Added support for "maps" cli command that displays meta information for various consistent maps in the system

Change-Id: I63e590a8520ac9d1238efe4ad0033dcba939e472
diff --git a/core/store/dist/src/main/java/org/onosproject/store/consistent/impl/DefaultDatabaseState.java b/core/store/dist/src/main/java/org/onosproject/store/consistent/impl/DefaultDatabaseState.java
index 837852d..e63a3d8 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/consistent/impl/DefaultDatabaseState.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/consistent/impl/DefaultDatabaseState.java
@@ -19,6 +19,7 @@
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
@@ -71,6 +72,11 @@
     }
 
     @Override
+    public Set<String> tableNames() {
+        return new HashSet<>(tables.keySet());
+    }
+
+    @Override
     public int size(String tableName) {
       return getTableMap(tableName).size();
     }