Added am:app service stub.

Apparently nothing at all is known about this service...

src/core/hle/service/am_app.h

@@ -0,0 +1,27 @@
+// Copyright 2014 Citra Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include "core/hle/service/service.h"
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+// Namespace AM_APP
+
+namespace AM_APP {
+
+class Interface : public Service::Interface {
+public:
+    Interface();
+
+    /**
+     * Gets the string port name used by CTROS for the service
+     * @return Port name of service
+     */
+    std::string GetPortName() const override {
+        return "am:app";
+    }
+};
+
+} // namespace