PackageInfo's providers field is not null anymore

This should fix https://github.com/robolectric/robolectric/issues/1210 which I opened couple of weeks ago.
At the moment it only fills `ProviderInfo` with `name` and `authority` fields which were already present in the `ContentProviderData` class. I guess, it would be better to parse other `<provider>` fields from the manifest too and fill in the providers' information (and I could even do that), however, first I want to make sure I am doing everything the right way.
By the way, why making your own `ContentProviderData` class rather than shadowing `ProviderInfo`?