Using net.jodah.expiringmap.ExpiringMap for tracking ttl expiration of database entries.
Minor javadoc updates.
diff --git a/core/api/src/main/java/org/onlab/onos/store/service/ReadResult.java b/core/api/src/main/java/org/onlab/onos/store/service/ReadResult.java
index 943bc63..7aeddda 100644
--- a/core/api/src/main/java/org/onlab/onos/store/service/ReadResult.java
+++ b/core/api/src/main/java/org/onlab/onos/store/service/ReadResult.java
@@ -22,6 +22,7 @@
 
     /**
      * Returns the status of the read operation.
+     * @return read operation status
      */
     public ReadStatus status() {
         return status;