Added Host related memos.

Change-Id: Idbbce6a72b6f7fecc6691f2af68f4ce40b58ca34
diff --git a/core/store/trivial/src/main/java/org/onlab/onos/store/trivial/impl/SimpleHostStore.java b/core/store/trivial/src/main/java/org/onlab/onos/store/trivial/impl/SimpleHostStore.java
index 67ed050..bf99227 100644
--- a/core/store/trivial/src/main/java/org/onlab/onos/store/trivial/impl/SimpleHostStore.java
+++ b/core/store/trivial/src/main/java/org/onlab/onos/store/trivial/impl/SimpleHostStore.java
@@ -35,6 +35,7 @@
 import static org.onlab.onos.net.host.HostEvent.Type.*;
 import static org.slf4j.LoggerFactory.getLogger;
 
+// TODO: multi-provider, annotation not supported.
 /**
  * Manages inventory of end-station hosts using trivial in-memory
  * implementation.