api: Implement bucket notification. (#2271)

* Implement basic S3 notifications through queues

Supports multiple queues and three basic queue types:

1. NilQueue -- messages don't get sent anywhere
2. LogQueue -- messages get logged
3. AmqpQueue -- messages are sent to an AMQP queue

* api: Implement bucket notification.

Supports two different queue types

- AMQP
- ElasticSearch.

* Add support for redis

vendor/gopkg.in/olivere/elastic.v3/rescore.go

@@ -0,0 +1,44 @@
+// Copyright 2012-2015 Oliver Eilhard. All rights reserved.
+// Use of this source code is governed by a MIT-license.
+// See http://olivere.mit-license.org/license.txt for details.
+
+package elastic
+
+type Rescore struct {
+	rescorer                 Rescorer
+	windowSize               *int
+	defaultRescoreWindowSize *int
+}
+
+func NewRescore() *Rescore {
+	return &Rescore{}
+}
+
+func (r *Rescore) WindowSize(windowSize int) *Rescore {
+	r.windowSize = &windowSize
+	return r
+}
+
+func (r *Rescore) IsEmpty() bool {
+	return r.rescorer == nil
+}
+
+func (r *Rescore) Rescorer(rescorer Rescorer) *Rescore {
+	r.rescorer = rescorer
+	return r
+}
+
+func (r *Rescore) Source() (interface{}, error) {
+	source := make(map[string]interface{})
+	if r.windowSize != nil {
+		source["window_size"] = *r.windowSize
+	} else if r.defaultRescoreWindowSize != nil {
+		source["window_size"] = *r.defaultRescoreWindowSize
+	}
+	rescorerSrc, err := r.rescorer.Source()
+	if err != nil {
+		return nil, err
+	}
+	source[r.rescorer.Name()] = rescorerSrc
+	return source, nil
+}