LPS-33228 Applying StagedModel interface to RepositoryModel [Waiting for an aswer]

Hey Julio,

This is re-sending of this PR: https://github.com/juliocamarero/liferay-portal/pull/1384

I've applied the changes we have discussed.

I haven't changed the order of the setters though; since these classes does not have a service.xml equivalent like the DLFileEntry. For the DLFileEntry we have a clone in the DLFileEntryModelImpl but since it has a service.xml equivalent we can refer to that for a setter order. But in our case we don't have one like the ServiceContext, so it's ordered alphabetically.

Thanks,

Máté