REFS #147 + Introduced php-formatter

Hi,

I've cleaned all headers, we are ready for 2015.

Also, I've added a ``.php-formatter.yml`` file with the rules applied on BackBee core, ``php-formatter`` cli can understand this file and fix the issues: don't forget to apply it to every PR now.

I've fixed a test (why the master is green ? sounds weird at this point) and finaly updated the ``CONTRIBUTING.md`` file to add a ``Formatting`` category.

Regards,