add: fridges view, fridge+sensor class, plot function, generator for test data

app/fridge.py

@@ -0,0 +1,15 @@
+class Fridge:
+
+    def __init__(self, name):
+        self.name = name.decode('utf-8')
+        self.sensors = list()
+
+    def add_sensor(self, sensor):
+        self.sensors.append(sensor)
+
+
+class Sensor:
+
+    def __init__(self, name, sensorid):
+        self.name = name.decode('utf-8')
+        self.id = sensorid