Add a `--chunkSize` param when using `--asTask`

[jalendport]

Created by Andrew Welch (@khalwat) on 04/02/18

Add the ability to group the tasks into chunks for processing, so a separate queue job isn't created for every step, but rather every chunk.

This would allow for running a queue job that processes, say, 10 elements at once or such, and could reduce some unnecessary overhead.