Minimal app

- Add navigation with reactnavigation: https://github.com/react-community/react-navigation
- Add NativeBase dep (start using components from this later)
- Add basic about screen
- Add basic membership purchase screen

android/app/src/main/java/no/neuf/chateau/MainActivity.java

@@ -0,0 +1,15 @@
+package no.neuf.chateau;
+
+import com.facebook.react.ReactActivity;
+
+public class MainActivity extends ReactActivity {
+
+    /**
+     * Returns the name of the main component registered from JavaScript.
+     * This is used to schedule rendering of the component.
+     */
+    @Override
+    protected String getMainComponentName() {
+        return "Dusken";
+    }
+}