Adding option to specify that the manifest is required.
- Fixing the error handling to load the commands.
- Exchange error handling in cli that formats the errors of the type AzkError.
Changing default node image.
Adding support system instances including exited instances.
Adding exception attempt to obtain a required system but not found in a manifest.
Refactoring cmd exec to make better use manifest.
Adding initial code for cmds: start, stop, scale, status