balooctl status: Produce parseable output

Summary:

• introduced -f|--format command-line option
• implemented formatters 'simple', 'json', 'multiline' (=current output)

Test Plan:
$ balooctl status -h
$ balooctl status /existing/path/* /not/existing/path [--format xxx]
JSON well-formed check:
$ balooctl status /existing/path/* /not/existing/path -f json | jq '.'

Reviewers: Frameworks, vhanda, smithjd, lbeltrame

Reviewed By: lbeltrame

Subscribers: broulik, ngraham

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D9958