Codeception test adjustments for basic and advanced applications

- Moved everything test-related into `tests` directory. Codeception tests are in `codeception`.
- Removed database module since we're using fixtures and migrations.
- Moved console entry points and bootstrap into `tests/codeception/bin`.
- Adjusted travis build scripts.
- Adjusted documentation to be consistent and reflect changes made.

apps/advanced/tests/codeception/common/_bootstrap.php

@@ -0,0 +1,16 @@
+<?php
+
+defined('YII_DEBUG') or define('YII_DEBUG', true);
+
+defined('YII_ENV') or define('YII_ENV', 'test');
+
+defined('ROOT_DIR') or define('ROOT_DIR', dirname(dirname(dirname(__DIR__))));
+
+require_once(ROOT_DIR . '/vendor/autoload.php');
+require_once(ROOT_DIR . '/vendor/yiisoft/yii2/Yii.php');
+require(ROOT_DIR . '/common/config/aliases.php');
+
+// set correct script paths
+$_SERVER['SERVER_NAME'] = 'localhost';
+
+Yii::setAlias('@codeception', dirname(__DIR__));