Added to the introduction that the Service Builder-generated layers provide the developer with a clean separation of concerns.

We discuss dependency injection a little bit when we list the Spring beans injected into the *LocalServiceBaseImpl classes. I think we also discuss that Hibernate's ORM allows Liferay services to be database-agnostic. I'll circle back to add to details on these topics in separate paragraphs.

I didn't want to list files in this section since this section is just supposed to provide a high level-overview of the benefits of using Service Builder vs other solutions for accessing databases.