multiple updates

- colour theme implemented. ThemeService based global switching for future light detection triggers
- test flipflop service for various fun
- navigator widget class with state switching

extra/themes/default.json

@@ -0,0 +1,14 @@
+{
+  "dark": {
+    "background": "#000000",
+    "foreground": "#FFFFFF",
+    "highlight": "#FF5555",
+    "subdued": "#808080"
+  },
+  "bright": {
+    "background": "#F0F0F0",
+    "foreground": "#1A1A1A",
+    "highlight": "#CC0000",
+    "subdued": "#606060"
+  }
+}