Add support for replicated-job

[douglascamata]

This PR adds support for replicated-job Services, which was pretty straight forward to add.

global-job mode seems to already work. I am successfully using it in a Docker Swarm cluster, but only with 1 node so take it with a grain of salt. I think the force update is what makes it work.

[manyhats492]

Based on how replicated-job functions, there should be no need for a specific label of swarm.cronjob.replicas. The user should be using the --replicas and --max-concurrent flags when using replicated-job. I think the amount of code changes could be reduced here.