Added method propertyName to GraphProperty annotation to explicitly set node property names.

Example: 

<pre><code>@NodeEntity
@TypeAlias("ARTIST")
public class Artist extends IdentifiableEntity {
	@GraphProperty(propertyName = "first_name")
	private String firstName;

	@GraphProperty(propertyName = "second_name")
	private String secondName;
	
	@GraphProperty(propertyName = "last_name")
	private String lastName;
	
	public Artist() {
	}
}
</code></pre>

it will create a node labeled :ARTIST with the following properties:
- first_name,
- second_name,
- last_name

mapped to these bean properties respectively:
- firstName
- secondName
- lastName