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

main.go

@@ -77,6 +77,10 @@ func enableLoggers() {
 	enableConsoleLogger()
 	enableFileLogger()
 
+	// Adding new bucket notification related loggers.
+	enableAMQPLogger()
+	enableElasticLogger()
+
 	// Add your logger here.
 }