Add test autoloader

Third-party users that require SMW as integration platform should add the following to their `bootstrap.php`.

```
$autoloader = require __DIR__ . '/../../SemanticMediaWiki/tests/autoloader.php'

$autoloader->addPsr4( ... );
```
### Follow-up

Instead of packages assuming that classes (such as`SMW\Test\QueryPrinterTestCase`) are freely available, the test environment should explicit invoke the autoloader to gain access to required objects.

- [ ] SemanticResultFormts
- [ ] SemanticMaps
- [ ] SemanticGlossary