Implement -q/--brief option (fixes #19) (#20) #78

Job	Run time
cargo fmt --all -- --check	7s
cargo check (ubuntu-latest)	20s
Code Coverage (ubuntu-latest, unix)	1m 25s
cargo clippy -- -D warnings (ubuntu-latest)	8s
cargo check (macOS-latest)	12s
GNU test suite	15s
Code Coverage (macos-latest, macos)	1m 17s
cargo check (windows-latest)	1m 7s
cargo clippy -- -D warnings (macOS-latest)	9s
Code Coverage (windows-latest, windows)	1m 2s
cargo clippy -- -D warnings (windows-latest)	1m 5s
cargo test (ubuntu-latest)	40s
cargo test (macOS-latest)	2m 6s
cargo test (windows-latest)	1m 46s
	11m 39s

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