- added list pipelines command
- cleaned up load pipelines method
- first filter can now bind to a direct exchange (routing key is optional)
- minor bug fixed: the 'internal' producer created an unnecessary anonymous queue for every consumer, removed.
  the producer now only creates a topic exchange where the filters can publish their results, and the next filter can pick it up.
- added purge pipeline command: purges all the queues of the pipeline
- filters are now using the queue in exclusive mode
- added durable and auto_delete options: queues and exchanges in the pipeline can be created with the durable and/or auto_delete flag
- replaced console output from echo to the dedicated method, and added a notice if the pipeline to be purged has not been found
- list pielines: replaced echo with writeln method
- cleaned up sendToNext and setProducer methods
- added error handling to pipeline filter
- documented the pipelines