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
It's not really important but i would prefer something like:

```php
} catch (ClassNotFoundException $e) { /* nothing to do */ }
```
or
```
} catch (ClassNotFoundException $e) { 
    /* nothing to do */ 
}
```
but not a mix of both syntax, what you think about it @mickaelandrieu?