Add more switches to enable/disable carrier features

Add bools to enable/disable the following carrier specific features:
- Exit menu item with 'Minimize or quit' dialog
- Display page title instead of URL in URL bar
- Allow users to provide custom download path
Add method to detect if a carrier specific feature is enabled.

Change-Id: I9db1b16afd14e476de474e8c86bd60ba1a450aba
diff --git a/res/xml/general_preferences.xml b/res/xml/general_preferences.xml
index 7c21b3a..361afde 100644
--- a/res/xml/general_preferences.xml
+++ b/res/xml/general_preferences.xml
@@ -142,7 +142,8 @@
             android:title="@string/pref_accessibility_title" />
 
 
-        <PreferenceScreen android:title="@string/pref_content_title">
+        <PreferenceScreen android:title="@string/pref_content_title"
+            android:key="content_settings">
             <CheckBoxPreference
                 android:defaultValue="true"
                 android:key="block_popup_windows"