Signed-off-by: Roeland Jago Douma <roeland@famdouma.nl>

Signed-off-by: Roeland Jago Douma <roeland@famdouma.nl>

Signed-off-by: Morris Jobke <hey@morrisjobke.de>

Signed-off-by: Lukas Reschke <lukas@statuscode.ch>

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

* Move a-b to PSR-4

* Move c-d to PSR-4

* Move e+g to PSR-4

* Move h-l to PSR-4

* Move m-r to PSR-4

* Move s-u to PSR-4

* Move files/ to PSR-4

* Move remaining tests to PSR-4

* Remove Test\ from old autoloader

Fixes https://github.com/owncloud/core/issues/19438

This change allows AppFramework applications to specify a custom CSP header for example when the default policy is too strict. Furthermore this allows us to partially migrate away from CSS and allowed eval() in our JavaScript components.

Legacy ownCloud components will still use the previous policy. Application developers can use this as following in their controllers:
```php
$response = new TemplateResponse('activity', 'list', []);
$cspHelper = new ContentSecurityPolicyHelper();
$cspHelper->addAllowedScriptDomain('www.owncloud.org');
$response->addHeader('Content-Security-Policy', $cspHelper->getPolicy());
return $response;
```

Fixes https://github.com/owncloud/core/issues/11857 which is a pre-requisite for https://github.com/owncloud/core/issues/13458 and https://github.com/owncloud/core/issues/11925

fix docstrings

adjust copyright date

another copyright date update

another header update

implement third headers argument, fix indention, fix docstrings

fix docstrings