Add plan only mode

Motivation

As a hash core developer, I want to add a CLI flag that only generates a plan without executing it, also with the possibility to save/display the plan.

Current state

There is no way to only do a plan without executing it.

Desired state

We have a flag to only plan and print or save the plan.

Steps

• Add a new CLI flag for plan only and use it in execute/main modules.
• Print the actions that would have been run if plan was executed.
• Save the graph using the dot format. Use this library to help.