Added a receiver to listen to app uninstalls

OpenKeychain/src/main/AndroidManifest.xml

@@ -110,6 +110,13 @@
                 <action android:name="org.torproject.android.intent.action.STATUS"/>
             </intent-filter>
         </receiver>
+        <!-- broadcast receiver for listening to package uninstalls -->
+        <receiver android:name=".remote.PackageUninstallReceiver">
+            <intent-filter>
+                <action android:name="android.intent.action.PACKAGE_FULLY_REMOVED" />
+                <data android:scheme="package"/>
+            </intent-filter>
+        </receiver>
         <!-- singleTop for NFC dispatch, see SecurityTokenOperationActivity -->
         <activity
             android:name=".ui.MainActivity"