Adding Manage External Sources Settings

Added a settings fragment to manage external sources. It lists all
applications that have either requested REQUEST_INSTALL_PACKAGES or have
their app op changed from default.

Test: Will include in follow-up CL. Tracked in b/33792674

Bug: 31002700
Change-Id: Ibd2a1922be214b62aec4eefa45f7b9691256b205
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index ed511ef..41db2eb 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -2905,6 +2905,17 @@
                 android:value="com.android.settings.applications.ManageApplications" />
         </activity>
 
+        <activity android:name="Settings$ManageExternalSourcesActivity"
+                android:label="@string/install_other_apps"
+                android:taskAffinity="">
+            <intent-filter android:priority="1">
+                <action android:name="android.settings.action.MANAGE_EXTERNAL_SOURCES" />
+                <category android:name="android.intent.category.DEFAULT" />
+            </intent-filter>
+            <meta-data android:name="com.android.settings.FRAGMENT_CLASS"
+                android:value="com.android.settings.applications.ManageApplications" />
+        </activity>
+
         <activity android:name="Settings$AppWriteSettingsActivity"
                 android:label="@string/write_settings_title"
                 android:taskAffinity="">