Added "Property" annotation to explicitly set Node property names

(something similar to @Column annotation in Hibernate).

Example: 

@NodeEntity
public class Artist extends IdentifiableEntity {

	@Property(name = "first_name")
	private String firstName;

	@Property(name = "last_name")
	private String lastName;
	
    public Artist() {
    }

    public Artist(String firstName, String lastName) {

        this.firstName = firstName;
        this.lastName = lastName;
    }
}