Currently there is no AppFramework way to modify cookies, which makes it unusable for quite some use-cases or results in untestable code.
This PR adds some basic functionalities to add and invalidate cookies.
Usage:
```php
$response = new TemplateResponse(...);
$response->addCookie('foo', 'bar');
$response->invalidateCookie('foo');
$response->addCookie('bar', 'foo', new \DateTime('2015-01-01 00:00'));
```
Existing cookies can be accessed with the AppFramework using `$this->request->getCookie($name)`.
fix docstrings
adjust copyright date
another copyright date update
another header update
implement third headers argument, fix indention, fix docstrings
fix docstrings
Lukas Reschke
Bernhard Posselt
Georg Ehrke
Bernhard Posselt
Thomas Tanghus
Thomas Müller