Integrate QR Code library instead of requiring the app to be installed, also due to security reasons

OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/QrCodeScanActivity.java

@@ -78,7 +78,11 @@ public class QrCodeScanActivity extends FragmentActivity {
             // scan using xzing's Barcode Scanner and return result parcel in OpenKeychain
 
             returnResult = true;
-            new IntentIntegrator(this).initiateScan();
+            IntentIntegrator integrator = new IntentIntegrator(this);
+            integrator.setDesiredBarcodeFormats(IntentIntegrator.QR_CODE_TYPES)
+                    .setPrompt(getString(R.string.import_qr_code_text))
+                    .setResultDisplayDuration(0)
+                    .initiateScan();
         } else if (ACTION_QR_CODE_API.equals(action)) {
             // scan using xzing's Barcode Scanner from outside OpenKeychain
 
@@ -168,7 +172,7 @@ public class QrCodeScanActivity extends FragmentActivity {
                         return;
                     }
 
-                    if ( ! result.success()) {
+                    if (!result.success()) {
                         // only return if no success...
                         Intent data = new Intent();
                         data.putExtras(returnData);