Tweet daily starred events

Each starred event in a single tweet.
Starting at 18:00 o'clock in X minutes intervals.
(Configure to re-post tweets to facebook)

cc @NicolasSchmutz @christopheschwyzer 

Depends on https://github.com/cargomedia/CM/issues/1257
Use like:
```php
$serviceManager = CM_Service_Manager::getInstance();
/** @var Denkmal_Twitter_Client $twitter */
$twitter = $serviceManager->get('twitter', 'Denkmal_Twitter_Client');

$eventTweeter = new Denkmal_Twitter_EventTweeter($twitter, new CM_Frontend_Render());
$eventTweeter->tweetStarredEvents(Denkmal_Site::getCurrentDate());
```