Add this extension to the Zikula Extension Library

#### Hi @cmfcmf-test!

You requested to add this extension to the [Zikula Extension Library](http://zikula.org/library/) :star:. You're just two clicks away from there:
1. Merge this PR!
2. Add a new Tag as version 1.0.0 (either using the git command line, your favourite git client or the [GitHub online interface](https://github.com/cmfcmf-test/EL1-4-PSR-4/releases/new))!

In case something doesn't work as expected, feel free to open an issue in the [Extension Library repository](https://github.com/craigh/ExtensionLibrary/issues/new)!