[RFR] - 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
o_O this is gonna crazy :dancer: 

I know php-cs-fixer is customisable but I don't how to do. Maybe in another issue ?