Current behavior:
Currently, rule action is a Go function.

Expected behavior:
Able to configure a flogo activity as a rule action, so that it gets invoked when the rule fires.

What is the motivation / use case for changing the behavior?
This allows rules application to send events/messages to external applications by leveraging various flogo activities readily available (ex: rest, kafka, etc...)

Additional information you deem important (e.g. I need this tomorrow):