v0.20.0

• Support writing to stdout in the pull command and in the sink step when - is specified as the db
• Support reading from stdin in the pull command when - is specified as the source
• Support reading from stdin in generator and html steps when - is specified as the source
• Add a --def argument to the flow command to provide or override the flow definition
• Add a --use-free-ports argument to the flow command
• (breaking) Rename sink-all-events property to sink-control-events. sink-all-events is still recognized as an alias.
• Add --sink-all-events argument to flow and pull commands
• Emit other event types (like control) from sqlite dbs in generator step