change preProcess from private to public

I need to override the preProcess method from a child class.

The use case is related to package renaming in a private satis repository. I understand the implication for packagist (and other public repository) but keeping the root packageName cause problem when you need to rename a package.

I will override override the name assignation with this

```PHP

// use the main identifier if name is not present
$data['name'] = !isset($data['name']) ? $this->packageName : $data['name'];

```
Merge pull request #3383 from mpoiriert/patch-1

change preProcess from private to public