Enhancements to work with shell script wrappers

[PinkPandaKatie]

I would like the ability to create a shell script that can call jira-cli to create an issue, then do things with the resulting key. I currently have to create a temporary file, tee the output to that file, then sift through the file to extract the key. It would be much easier if there were some way to export data to a shell script.

A possible solution would be to add a --shell option, which would:
a. Cause all terminal output to go to STDERR instead of STDOUT
b. Write resulting data in shell variable format, e.g.

NEW_ISSUE_KEY='PROJ-123'
NEW_ISSUE_URL='https://jira.company.com/browse/PROJ-123'

This would allow shell scripts to do:

eval "`jira issue create --shell -tRequest ...`"

and automatically get the results.