Add configuration discovery helper method

Sensor configuration is passed to the application via the enviroment.
Create a map of environment values for a given sensor.

Change-Id: I8369eda27798fd9472166e898b8d6166c6997392
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/Makefile.am b/Makefile.am
index 1f5b6ca..8340c05 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -12,6 +12,7 @@
 	sensorset.cpp \
 	mainloop.cpp \
 	sysfs.cpp \
+	env.cpp \
 	xyz.openbmc_project.Sensor.Value.cpp \
 	xyz.openbmc_project.Sensor.Threshold.Warning.cpp \
 	xyz.openbmc_project.Sensor.Threshold.Critical.cpp