removed old code: - removed gateway which was an HTTP gateway inherited from Idavoll and which is not used is SàT Pubsub - removed memory_storage which has not been maintained since Idavoll and which is expected to be replaced by a sqlite-based backend - simplejson dependency is not used anymore

create table callbacks (
    service text not null,
    node text not null,
    uri text not null,
    PRIMARY KEY (service, node, uri)
);