Fixes #6103: Improved codeception config in app templates to ease testing of advanced app on multiple hosts

Fixes #4827: default config for functional tests of both basic and advanced app now turns off CSRF validation while providing commented out alternative setting cookie domain to localhost

Used a single database and a single CLI entry point for all test types. Added faker to basic app dev requirements.

Exposed basic app entry URL via codeception.yml, refactored configs of advanced app to read from config and define entry script in a single place

- 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.

- Removed hacks since these are no longer required: https://github.com/Codeception/Codeception/commit/71db233985531f298264dc4ca0160d2aa1c83b7f
- Removed unused helper classes
- Added 2.0 style "actor" to config

Thanks to @Ragazzo and @DavertMik for helping with it.

Fixes #4071: `mail` component renamed to `mailer`, `yii\log\EmailTarget::$mail` renamed to `yii\log\EmailTarget::$mailer`

This reverts commit 2bb6f135.