Add Average and Maximum classes

These classes will implement the
xyz.openbmc_project.Sensor.Aggregation.History.Average/Maximum
interfaces.   Each of these interfaces contains an array of
value/timestamp entries, where the value is either the average
or maximum power as reported by the power supply.  The most recent
value will always be in element 0 of the array.

Change-Id: I41b0b84abe146c57f23629bd50acbf9e7fb746ab
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/Makefile.am b/Makefile.am
index 87250db..8fa771c 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -6,11 +6,13 @@
 	-lstdc++fs \
 	$(PHOSPHOR_LOGGING_LIBS) \
 	$(SDBUSPLUS_LIBS) \
-	$(PHOSPHOR_DBUS_INTERFACES_LIBS)
+	$(PHOSPHOR_DBUS_INTERFACES_LIBS) \
+	$(OPENPOWER_DBUS_INTERFACES_LIBS)
 libpower_la_CXXFLAGS = \
 	$(PHOSPHOR_LOGGING_CFLAGS) \
 	$(SDBUSPLUS_CFLAGS) \
-	$(PHOSPHOR_DBUS_INTERFACES_CFLAGS)
+	$(PHOSPHOR_DBUS_INTERFACES_CFLAGS) \
+	$(OPENPOWER_DBUS_INTERFACES_CFLAGS)
 
 libpower_la_SOURCES = \
 	gpio.cpp \