Added docker as a build target

[retgits]

Added docker as a build target

flogo build -e -docker trigger_id

This will create a minimal dockerfile in the bin directory and execute docker build on that file to store it in the current user's docker registry

[retgits]

Hi @mellistibco, thanks for the feedback! I've updated the code accordingly 😄

[mellistibco]

Another suggestion, what about if no trigger is specified? That should be allowed and there just wont be any ports exposed

[retgits]

The flag "-docker" is a string because we need to support a command line argument to specify the trigger id. Because the type is a string it expects a value to be set, otherwise it will throw an error. What I've done is if you run flogo build -e -docker no-trigger it will assume you don't need to expose an HTTP port