sensor-mon: Threshold alarm logger framework

Add the new class ThresholdAlarmLogger that will watch the Warning,
Critical, and PerformanceLoss sensor threshold D-Bus interfaces and
create event logs when their alarm properties set and clear.

This commit just creates the class with its three sdbusplus match
objects to watch those interfaces.

Change-Id: I67c629bcabe059952c2029dc034daace9b88f051
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/sensor-monitor/Makefile.am b/sensor-monitor/Makefile.am
index da19997..313c59f 100644
--- a/sensor-monitor/Makefile.am
+++ b/sensor-monitor/Makefile.am
@@ -9,6 +9,7 @@
 
 sensor_monitor_SOURCES = \
     shutdown_alarm_monitor.cpp \
+    threshold_alarm_logger.cpp \
 	main.cpp
 
 sensor_monitor_LDADD = \