All tools should offer JSON output format

Several recent tools (including listcaslibs.py, listcastables.py, listcaslibsandeffectiveaccess.py, listcastablesandeffectiveaccess.py and listgroupsandmembers.py) only output text, in CSV format.

As a general design goal, it would be preferable for all pyviyatools to have at least an option to output JSON rather than text.

Any views on whether one or the other needs to universally be the default? Or are we happy for some to default to JSON, some to CSV text, and so on depending on what job they were developed to do?

Could also split this issue into one per tool, to make tracking completion easier. I haven't yet because that would create a lot of issues and perhaps one is enough.