Composer Support and minor additions

This Pull Request adds the possibility to install project dependencies via [Composer](https://getcomposer.org/).
The command `make install-composer` can be used as a shortcut.

This should work as soon as https://github.com/AKSW/Erfurt/pull/86 is merged and Erfurt is registered at [Packagist](https://packagist.org/).

You might want to register [RDFauthor](https://github.com/AKSW/RDFauthor) at Packagist as well, to avoid the inline package definition in OntoWiki.

The following additional changes have been made:

- Replaced some Short Tags as the [OntoWiki documentation](https://github.com/AKSW/OntoWiki/wiki/php.ini-recommendations) recommends to avoid them
- Avoided serialization of huge object graphs (for example Zend_View object)
- Made news feed URL configurable, for example useful for offline presentations