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/basic/tests/codeception/_bootstrap.php

@@ -0,0 +1,23 @@
+<?php
+
+// the entry script URL (without host info) for functional and acceptance tests
+// PLEASE ADJUST IT TO THE ACTUAL ENTRY SCRIPT URL
+defined('TEST_ENTRY_URL') or define('TEST_ENTRY_URL', '/index-test.php');
+
+// the entry script file path for functional and acceptance tests
+defined('TEST_ENTRY_FILE') or define('TEST_ENTRY_FILE', dirname(dirname(__DIR__)) . '/web/index-test.php');
+
+defined('YII_DEBUG') or define('YII_DEBUG', true);
+
+defined('YII_ENV') or define('YII_ENV', 'test');
+
+require_once(__DIR__ . '/../../vendor/autoload.php');
+
+require_once(__DIR__ . '/../../vendor/yiisoft/yii2/Yii.php');
+
+// set correct script paths
+$_SERVER['SCRIPT_FILENAME'] = TEST_ENTRY_FILE;
+$_SERVER['SCRIPT_NAME'] = TEST_ENTRY_URL;
+$_SERVER['SERVER_NAME'] = 'localhost';
+
+Yii::setAlias('@codeception', __DIR__);