BDD User Group operations

These changes are implementations of BDD's 'Given' Steps for creating and removing User Groups.
These functions will traverse the User Groups tree and create and / or delete specific User Group(s) depending on if they are or are not found before, in the tree.
Again, code repetition.

Something like the bellow would be cleaner:
```
$this->createUserGroup( $name, $parentUserGroup );
```