QueueInterface is DALMP interface to be use with the DALMP\Queue class.
The common methods are:
|enqueue($key)||Adds an element to the queue.|
|dequeue($limit = false)||Dequeues an element from the queue.|
|delete($key)||Delete an element from the queue.|
|X()||Return the queue object.|
All the queue backends must implement this interface in order to properly work with DALMP.
The construct for each queue backend maybe be different and it is used for defining specific options like the host, port, path etc,
.. seealso:: `PHP Object Interfaces <http://www.php.net/manual/en/language.oop5.interfaces.php>`_.