REFS #143 - use BackBee/Utils inside BackBee

* Applied php-cs-fixer
* Removed unused classes (which have been moved to ``utils`` library
* Use ``utils`` library inside project, updated namespaces and composer.json
Is it recommended to have no whitespace between concatenation operator ``.`` and its operands? I'm not sure about it but i remember that in PSR recommandation we must have whitespace before and after operator just like ``+`` ``-`` etc.