Make visible the queue size and inform there is a queue

[everton137]

Sometimes users of the open spending platform don't know why it keeps always analysing a loaded data. This can happen when there is a big queue.

Informing the user the queue size, even that now we cannot predict the time to load all queues, can be useful for the user understand there is a queue and which position is his or her dataset.

[everton137]

Per @tryggvib at #openspending, a message like "Your dataset has been added to the queue. There are 2500 items in the queue" would be great.