Create channel pattern example

[pointlander]

Channels allow one action to call another action. Create an example using this pattern:
https://github.com/project-flogo/microgateway/blob/master/internal/pattern/DefaultChannelPattern.json
The example will call another microgateway action (in the same flogo application/json file/go file) using channels. The called microgateway action can be as simple as a call to the log activity. Two triggers will be needed: a http trigger for calling the channel pattern, and a channel trigger for calling the second microgateway:
https://github.com/project-flogo/contrib/tree/master/trigger/channel