use ACardEmulator as nfc backend for pcsc-relay

This feature is experimental and disabled by default

At ACardEmulator's compile time it is required:
- to add the correct application identifier to aid_list.xml
- enable the connection to pcsc-relay by setting useVPCD

ACardEmulator/app/src/main/res/xml/aid_list.xml

@@ -19,4 +19,9 @@
     <aid-group android:description="@string/applet_isoapplet" android:category="other">
         <aid-filter android:name="@string/aid_isoapplet"/>
     </aid-group>
+
+    <aid-group android:description="@string/applet_paccess" android:category="other">
+        <aid-filter android:name="@string/aid_paccess"/>
+    </aid-group>
+
 </host-apdu-service>