Other stasher::client->name_request()s

stasher::getdir_request(), stasher::subscribe_request() and stasher::subscribeserverstatus_request() follow the same design as other asynchronous requests, like stasher::get_request() and stasher::put_request(), and implement the asynchronous versions of their synchronous cousins; and can be used, in the same way, with stasher::process_request().