DATAJPA-466 - Add support for lazy loading configuration via JPA 2.1 fetch-/loadgraph.

We now support load-graph / fetch-graph QueryHints on repository query methods, which are applied when a JPA 2.1 capable JPA implementation is used. We explicitly reject the usage of those hints in case the user is running a JPA 2.0 provider.

FetchGraphs / LoadGraphs can now be defined on the Entity via the @NamedEntityGraphs annotation.

@Entity
@QueryEntity
@NamedEntityGraphs(@NamedEntityGraph(name = "GroupInfo.members", attributeNodes = @NamedAttributeNode("members")))
public class GroupInfo {

  @ManyToMany List<GroupMember> members = new ArrayList<GroupMember>(); //default fetch mode is "lazy".
}

The entity graph "GroupInfo.members" overwrites the fetch-mode of the members collection to be "eager".

The entity graph to be used can now configured on a repository query method.

@Repository
public interface GroupRepository extends CrudRepository<GroupInfo, String> {

	@EntityGraph("GroupInfo.members")
	GroupInfo getByGroupName(String name);
}

The new method JpaQueryMethod#getEntityGraph analyses an @EntityGraph annotation and constructs a new JpaEntityGraph value object that contains the information form the annotation. The new method AbstractJpaQuery#applyEntityGraphConfiguration tries to apply the given EntityGraph configuration if the used JPA persistence provider supports the JPA 2.1 spec.

Changed the class path order such that EclipseLink is now placed before the eclipse dependency. EclipseLink references the JPA 2.1 API and allows us to provide type-safe support for the new JPA 2.1 features.

Original pull request: #74.