add activity for android-specific initialization

This is work towards #23. Unfortunately, due to javafxports/android
[#73](https://bitbucket.org/javafxports/android/issues/73/hardware-button-key-events-report)
and
[#75](https://bitbucket.org/javafxports/android/issues/75/fxactivity-does-not-call),
there is no way to control volume. However, this *should* work once #75 is
fixed.

app/src/android/AndroidManifest.xml

@@ -23,14 +23,18 @@
     <meta-data android:name="com.google.android.gms.version"
         android:value="@integer/google_play_services_version" />
     <activity
-        android:name="javafxports.android.FXActivity"
+        android:name="org.gamefolk.roomfullofcats.CatsActivity"
         android:label="@string/app_name"
         android:screenOrientation="portrait" >
-      <meta-data android:name="main.class" android:value="org.gamefolk.roomfullofcats.RoomFullOfCatsApp" />
+      <meta-data android:name="main.class" android:value="org.gamefolk.roomfullofcats.CatsActivity" />
       <intent-filter>
         <action android:name="android.intent.action.MAIN" />
         <category android:name="android.intent.category.LAUNCHER" />
       </intent-filter>
     </activity>
+    <activity android:name="javafxports.android.FXActivity"
+              android:screenOrientation="portrait">
+      <meta-data android:name="main.class" android:value="org.gamefolk.roomfullofcats.RoomFullOfCatsApp" />
+    </activity>
   </application>
 </manifest>

app/src/android/java/org/gamefolk/roomfullofcats/CatsActivity.java

@@ -0,0 +1,31 @@
+package org.gamefolk.roomfullofcats;
+
+import android.app.Activity;
+import android.content.Intent;
+import android.media.AudioManager;
+import android.os.Bundle;
+
+import javafxports.android.FXActivity;
+
+import java.util.logging.Logger;
+
+/**
+ * Shim class that immediately passes control to FXActivity.
+ *
+ * We use this to perform any Android-specific initialization.
+ */
+public class CatsActivity extends Activity {
+
+    private static final Logger Log = Logger.getLogger(RoomFullOfCatsApp.class.getName());
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        // This should work, once javafxports/android #73 and #75 are fixed.
+        setVolumeControlStream(AudioManager.STREAM_MUSIC);
+
+        Intent intent = new Intent(this, FXActivity.class);
+        startActivity(intent);
+    }
+}