Add time Manager to handle property changes callback

1. Implement time::Manager who registers property change signal for time
mode and owner;
2. Add PropertyChangeListner interface to handle the callback;
3. Make EpochBase to implement the interface.

Change-Id: I185580ae37353e1ed82a47e4905fb22e269ac09d
Signed-off-by: Lei YU <mine260309@gmail.com>
diff --git a/test/TestHostEpoch.cpp b/test/TestHostEpoch.cpp
index dca8d72..ec8ecf1 100644
--- a/test/TestHostEpoch.cpp
+++ b/test/TestHostEpoch.cpp
@@ -3,6 +3,7 @@
 
 #include "host_epoch.hpp"
 #include "config.h"
+#include "types.hpp"
 
 namespace phosphor
 {
@@ -15,9 +16,6 @@
 class TestHostEpoch : public testing::Test
 {
     public:
-        using Mode = EpochBase::Mode;
-        using Owner = EpochBase::Owner;
-
         sdbusplus::bus::bus bus;
         HostEpoch hostEpoch;