Add CommandClassNotFoundException

- Pass registered namespaces to exception
CommandLoader improvement
show possbile class names
CommandClassNotFoundException: Add accessor methods
trigger_error when users use registerCommand instead of addCommand.
replace registerCommand with addCommand
Add CommandGroup class
When using addCommandGroup, we should register the commands
automatically
Update doc block for addCommandGroup
Move addCommandGroup to CommandBase class
Add command group description
Add BuildGitHubWikiTopicsCommand class
use class name
Save Group objects into $class->commandGroups
Adjust level style
use logger object to output text
Adjust color to strong white
Improve help content printing
improvement with option printer
Count column width