Support for expiring Database entries

Registering database entry expiration tracker with DatabaseStateMachine

Support for publishing database state machine snapshot installation events.
Expiry tracker will listen to these events to bootstrap its local state.

Change-Id: I8bf22c8d7bab38624341350ccc083c5ca2fcb117
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/DatabaseClient.java b/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/DatabaseClient.java
index 77ff062..0021eb7 100644
--- a/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/DatabaseClient.java
+++ b/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/DatabaseClient.java
@@ -35,6 +35,16 @@
         }
     }
 
+    public boolean createTable(String tableName, int ttlMillis) {
+
+        CompletableFuture<Boolean> future = copycat.submit("createTable", tableName, ttlMillis);
+        try {
+            return future.get();
+        } catch (InterruptedException | ExecutionException e) {
+            throw new DatabaseException(e);
+        }
+    }
+
     public void dropTable(String tableName) {
 
         CompletableFuture<Void> future = copycat.submit("dropTable", tableName);