Add output streaming support to sensuctl

[echlebek]

Expected Behavior

When listing resources with sensuctl and using the --chunk-size option, I expect to receive each chunk as it arrives.

Current Behavior

The chunks are collated until there are no more chunks to bad had, before being output.

Possible Solution

Add output streaming support to sensuctl. This will necessitate rewriting much of the output formatting code, which is due for an overhaul in any case.

Steps to Reproduce (for bugs)

1. Try to output tens of thousands of resources with a small chunk size. (i.e. sensuctl event list --chunk-size 100)
2. Observe that the operation takes a long time to return any information.

[ccressent]

Some context: #2966

[calebhailey]

One of the comments in #2966 that caught my attention was RE: tabular output column widths, which is something I'd love to revisit. The way we render columns in certain sensuctl outputs today is quite cumbersome because we don't place any limits on the output (e.g. if an event has a very long output the columnar output of sensuctl event list is a mess). I'd love to see us adopt some sort of truncation, if not completely revisit the design of columnar list output.