[Atk14] Making a request in a test class is now a little bit easier

One can call $this->client->get("index") instead of $this->client->get("articles/index").
Both calls work the same as long as they are in tc_articles.php file.
Test fixed
[Atk14] A (PHP) namespace could be set in a form file

This helps avoid classname collisions in tests
e.g.
```php
<?php
// file: app/forms/spam_filters/index_form.php
namespace SpamFilters;
class IndexForm extends \ApplicationForm{
	// ...
}
```
[TableRecord] New method added: Cache::CachedIds()
[Logger] Logger is now configurable with constants