slurm

As requested in https://gitter.im/bd2k-genomics-toil/Lobby?at=617126297db1e3753e527ff2 it would be useful for debugging to be able to stop the whole workflow as soon as a single job fails, even if other jobs still exist to be run or are currently running.

┆Issue is synchronized with this Jira Task
┆Issue Number: TOIL-1062

Just like parallel::makePSOCKCluster() sets up a SOCKcluster object of SOCKnode workers, I think it would not be too complicated(*) to provide CMQcluster and CMQnode alternatives for clustermq.
For instance,

cl <- clustermq::makeClusterMCQ("sge")
y <- parallel::parLapply(1:10, FUN = sqrt)
parallel::stopCluster(cl)

(*) Roughly, S3 methods for generic functions such a