Added Billie payment method

src/molliebillie_devapp.php

@@ -0,0 +1,22 @@
+<?php
+
+require_once __DIR__ . '/mollie/mollie.php';
+
+function molliebillie_devapp_config()
+{
+    $config = mollie_config();
+
+    $config = array_merge($config, array(
+        'FriendlyName' => array(
+            'Type' => 'System',
+            'Value' => 'Mollie Billie'
+        )
+    ));
+
+    return $config;
+}
+
+function molliebillie_devapp_link($params)
+{
+    return mollie_link($params, \Mollie\Api\Types\PaymentMethod::BILLIE);
+}