Refactor Command class

Fix bug in domains check

Verbose output and refactorings

- Add simple config validation
- Add option to enable verbose output
- Tweak output, errors and notifications
- Refactor Command, exit codes and configuration

Formatting and little tweaks

Switch to cPanel UAPI

Refactor Command class and update readme

Better output and errors plus bugfixes

Fix parsing arguments

More command line arguments

Fix notifications