CLI Usability Enhancements

[sabre1041]

From a usability perspective, the current modctl CLI is focused on implementation rather than usability. In order to increase adoption and use, several areas within the CLI can be improved upon:

• Command and subcommand descriptions
• Helper functions
• Expanded high level explanation of the tool and use
• Messaging when errors are encountered

Each of these areas improve the user experience and encourage adoption of the project

[chlins]

Updated command descriptions in #256.