Move Java Blimp shell code to app subpackage

blimp/client/app/android/java/src/org/chromium/blimp/settings/Preferences.java

-// Copyright 2016 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-package org.chromium.blimp.settings;
-
-import android.app.Activity;
-import android.os.Bundle;
-
-/**
- * An activity to display the settings and version info.
- */
-public class Preferences extends Activity {
-    private static final String TAG = "Preferences";
-
-    @Override
-    public void onCreate(Bundle savedInstanceState) {
-        super.onCreate(savedInstanceState);
-        getFragmentManager()
-                .beginTransaction()
-                .replace(android.R.id.content, new AboutBlimpPreferences())
-                .commit();
-    }
-}