Make batch.id robust to warning messages from sbatch

[bwcompton]

I ran into a crazy bug today: getJobStatus gave me batch.id = "that". It turns out that when I requested a large amount of memory, sbatch returned this um, helpful message:

sbatch: INFO: Note that 128 GB per node will require a node with more than 128 GB memory 
because of overhead. Check https://docs.unity.rc.umass.edu/nodes for an appropriate limit.
Submitted batch job 38139957

clusterFunctionsSlurm was pulling the 4th word of the first line, which should have been the Slurm jobid, but instead was "that". It wanted, of course, the last line.

This really isn't a bug in batchtools, as the sysops inserted an informational message in a crazy place. But I suspect if the smart, on the ball people at the UMass Unity cluster are doing this, others probably are too. It'd be nice for batchtools to be robust to such shenanigans. Alternatively, I suppose it could throw an error if batch.id is non-numeric and print the message from sbatch.

My suggested change looks for a line beginning with "Submitted batch job" and pulls the 4th word as the batch.id.

I've tested this change against the following:

output <- 'Submitted batch job 12345678'
output <- 'This is a crazy informational message\nSubmitted batch job 98765432'
output <- 'This is crazy\nand uncalled for\nSubmitted batch job 5555555\nand even more stuff'

as well as against real-life submitJobs calls, both with and without the informational message.