Moved generic Timestamp/ClockManager classes to onos-api
so they are usable by applications.

Change-Id: Icf0e92d12434dec782332e91b632da8066a85b60
diff --git a/core/store/dist/src/main/java/org/onosproject/store/host/impl/HostClockManager.java b/core/store/dist/src/main/java/org/onosproject/store/host/impl/HostClockManager.java
index 097af85..f96568b 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/host/impl/HostClockManager.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/host/impl/HostClockManager.java
@@ -24,7 +24,7 @@
 import org.onosproject.net.HostId;
 import org.onosproject.net.host.HostClockService;
 import org.onosproject.store.Timestamp;
-import org.onosproject.store.impl.WallClockTimestamp;
+import org.onosproject.store.service.WallClockTimestamp;
 import org.slf4j.Logger;
 
 /**