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.

Fixes #4706

*TODO*

- [x] Adjust years.
- [x] Fix travis.
- [x] Move configs to `configs`?
- [ ] Add faker support to basic app.
- [x] Expose basic app URL in codeception.yml.
- [x] _log was renamed _output
- [x] _helpers was renamed _support
Maybe the string `/backend/web/index-test.php` should be placed into the `yml` file too?