Using 1.1.4-Final, I can't add any plugin because i get a 500 error with this message:

ERROR: null value in column "id" violates not-null constraint

So looks like that the hibernate_sequence is not being used to insert.
Looking at the PluginBean class, i see the following:

@Id @GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;

but maybe should be:

@Id @GeneratedValue(strategy = GenerationType.SEQUENCE)
private Long id;