Make LocalePicker Fragment.

The logic calling selectFirst() is removed as
- There's no comment why it is needed.
- Actually SetupWizard gets stack as that forces users to see
  WirelessSettings in SetupWizard.

The other changes:
- Move back LocalePickerFragment to LocalePicker.
- Make <activity> for LocalePicker in AndroidManifest <activity-alias>
- Add a short comment about how getComponent(), which should be a key
  for understanding how top-level settings work.
- Modify LanguageSettings so that it corectly points LocalePicker as
  a fragment.

Change-Id: I78d356e40af896ba1aab72fba12c90467371c7b0
diff --git a/res/xml/language_settings.xml b/res/xml/language_settings.xml
index edcfc6c..730d6ea 100644
--- a/res/xml/language_settings.xml
+++ b/res/xml/language_settings.xml
@@ -19,11 +19,9 @@
         android:title="@string/language_keyboard_settings_title">
 
     <PreferenceScreen
-            android:key="phone_language"
-            android:title="@string/phone_language">
-        <intent android:action="android.intent.action.MAIN"
-                android:targetPackage="com.android.settings"
-                android:targetClass="com.android.settings.LocalePicker"/>
+       android:fragment="com.android.settings.LocalePicker"
+       android:key="phone_language"
+       android:title="@string/phone_language">
     </PreferenceScreen>
 
     <PreferenceCategory android:key="text_category"