apphandler: Add storage for Get/Set System Info Parameter

All but one standard System Info Parameter and most (all?) OEM
parameters are string type. Add a interface to connect string callbacks
to System Info Parameter selector codes. Also add a convenience call
that can connect a static string to a parameter selector code.

Change-Id: I5e35d0418b8ddf5b2575fac093acfc7d7ca2217c
Signed-off-by: Xo Wang <xow@google.com>
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/Makefile.am b/Makefile.am
index 8286fd4..28ae7ed 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -70,6 +70,7 @@
 	app/watchdog.cpp \
 	app/watchdog_service.cpp \
 	apphandler.cpp \
+	sys_info_param.cpp \
 	sensorhandler.cpp \
 	storagehandler.cpp \
 	chassishandler.cpp \