Rewrite integration tests to run with Docker containers

tests/configs/config.postgres.php

@@ -0,0 +1,12 @@
+<?php
+
+define('DB_DRIVER', 'postgres');
+define('DB_USERNAME', 'postgres');
+define('DB_PASSWORD', 'postgres');
+define('DB_HOSTNAME', 'postgres');
+define('DB_NAME', 'kanboard');
+
+define('DEBUG', true);
+define('LOG_DRIVER', 'stderr');
+
+define('API_AUTHENTICATION_TOKEN', 'test');