rewrite property engine

Property class is gone; logic is now done with Layers, Stack and Filter

test/property/test_property_stack.py

@@ -0,0 +1,43 @@
+from unittest import TestCase
+from unittest.mock import Mock
+from owrx.property import PropertyLayer, PropertyStack
+
+
+class PropertyStackTest(TestCase):
+    def testLayer(self):
+        om = PropertyStack()
+        pm = PropertyLayer()
+        pm["testkey"] = "testvalue"
+        om.addLayer(1, pm)
+        self.assertEqual(om["testkey"], "testvalue")
+
+    def testHighPriority(self):
+        om = PropertyStack()
+        low_pm = PropertyLayer()
+        high_pm = PropertyLayer()
+        low_pm["testkey"] = "low value"
+        high_pm["testkey"] = "high value"
+        om.addLayer(1, low_pm)
+        om.addLayer(0, high_pm)
+        self.assertEqual(om["testkey"], "high value")
+
+    def testPriorityFallback(self):
+        om = PropertyStack()
+        low_pm = PropertyLayer()
+        high_pm = PropertyLayer()
+        low_pm["testkey"] = "low value"
+        om.addLayer(1, low_pm)
+        om.addLayer(0, high_pm)
+        self.assertEqual(om["testkey"], "low value")
+
+    def testLayerRemoval(self):
+        om = PropertyStack()
+        low_pm = PropertyLayer()
+        high_pm = PropertyLayer()
+        low_pm["testkey"] = "low value"
+        high_pm["testkey"] = "high value"
+        om.addLayer(1, low_pm)
+        om.addLayer(0, high_pm)
+        self.assertEqual(om["testkey"], "high value")
+        om.removeLayer(high_pm)
+        self.assertEqual(om["testkey"], "low value")