Device admin to prevent uninstall

Refs #92

app/src/main/AndroidManifest.xml

@@ -59,5 +59,17 @@
                 android:name="android.appwidget.provider"
                 android:resource="@xml/widget" />
         </receiver>
+
+        <receiver
+            android:name=".DeviceAdministratorReceiver"
+            android:permission="android.permission.BIND_DEVICE_ADMIN">
+            <meta-data
+                android:name="android.app.device_admin"
+                android:resource="@xml/admin" />
+            <intent-filter>
+                <action android:name="android.app.action.DEVICE_ADMIN_ENABLED" />
+                <action android:name="android.app.action.ACTION_DEVICE_ADMIN_DISABLED" />
+            </intent-filter>
+        </receiver>
     </application>
 </manifest>

app/src/main/java/eu/faircode/netguard/DeviceAdministratorReceiver.java

@@ -0,0 +1,41 @@
+package eu.faircode.netguard;
+
+/*
+    This file is part of NetGuard.
+
+    NetGuard is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    NetGuard is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with NetGuard.  If not, see <http://www.gnu.org/licenses/>.
+
+    Copyright 2015 by Marcel Bokhorst (M66B)
+*/
+
+import android.app.admin.DeviceAdminReceiver;
+import android.content.Context;
+import android.content.Intent;
+import android.util.Log;
+
+public class DeviceAdministratorReceiver extends DeviceAdminReceiver {
+    private static final String TAG = "NetGuard.Admin";
+
+    @Override
+    public void onEnabled(Context context, Intent intent) {
+        super.onEnabled(context, intent);
+        Log.i(TAG, "Device admin enabled");
+    }
+
+    @Override
+    public void onDisabled(Context context, Intent intent) {
+        super.onDisabled(context, intent);
+        Log.i(TAG, "Device admin disabled");
+    }
+}

app/src/main/res/xml/admin.xml

@@ -0,0 +1,3 @@
+<device-admin xmlns:android="http://schemas.android.com/apk/res/android" >
+    <uses-policies />
+</device-admin>