Added interval changes comprobation and differente queues in Service model.
Added interval changes comprobation and differente queues in Service model.

ADD: Multiple queue support
Added multiple queue support to give different priorities depending
of the service's priority.

ADD: Interval change check
Added to remove a scheduled job and add it again in order to make the change
successful at the moment.

odarriba/watchr,odarriba/watchr,odarriba/watchr