Fixing error with from() parameters in example

The from method requires $from and the $alias to be separate parameters.

    public function from($from, $alias, $indexBy = null);

The examples show: from('User u')
Merge pull request #1161 from gammamatrix/patch-1

Fixing error with from() parameters in example
DDC-3349: Possibility to override order of fields of composite ID produced by Mapping