Add verbose output to create-stack command about jam

[robdimsdale]

In addition to the docker output suggested in #83 , I would expect the --verbose command to print out each step that it is doing. Examples might include setting the default shell if it is not present in stack.toml and setting environment variables on the images.

[robdimsdale]

And, of course, there might be other commands where instrumentation is valuable, too.

[robdimsdale]

I'm going to close this issue because we haven't received any signal on it in almost a year. It could be valuable, and if we get more feedback about this then we can explore implementing it.