Add storeGroups/restoreGroups method to LED Manager

Use CEREAL to storeGroup/restoreGroups the current state of
asserted groups.
Call storeGroups() when the request comes to add to(remove from)
asserted group.
Call restoreGroups() as part of starting LED Manager daemon.

Tested: Manually set the Asserted property of each group to true,
after rebooting, all property values tested with the busctl command
are still true.

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: Ibeb1de5f51e3d67e98eeea34764e9efc6d6d8b35
diff --git a/Makefile.am b/Makefile.am
index 7f58aa3..60cac80 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -4,7 +4,8 @@
 phosphor_ledmanager_SOURCES = \
                 led-main.cpp  \
                 manager.cpp \
-                group.cpp
+                group.cpp \
+                serialize.cpp
 
 if !WANTS_JSON
 BUILT_SOURCES = led-gen.hpp