HHH-6895 : Easier annotation definition of increment generator

This commit is a fix so that it is possible to do:

@Id 
@GeneratedValue( generator="increment" )
public Long getId() { .. }

instead of:
@Id 
@GeneratedValue( generator="increment" )
@org.hibernate.annotations.GenericGenerator( name = "increment", strategy = "increment" )
public Long getId() { .. }