Use the user provided label instead of the machine generated name

for creating graphs when it is available (especially useful for zwave,
since the name then contains long numbers for the value id's)

houseagent/core/database.py

@@ -560,7 +560,7 @@ def query_values(self):
                                "LEFT OUTER JOIN history_periods ON (current_values.history_period_id = history_periods.id)")
 
     def query_values_light(self):
-        return self.dbpool.runQuery("SELECT id, name, history_period_id, history_type_id FROM current_values;")
+        return self.dbpool.runQuery("SELECT id, IFNULL(label, name), history_period_id, history_type_id FROM current_values;")
 
     def query_devices(self):      
         return self.dbpool.runQuery("SELECT devices.id, devices.name, devices.address, plugins.name, locations.name from devices " +