Command descriptor refactoring

Hi,

To easily add configurations when commands are declared, we redefined the addCommand method. Now, this method take one object in parameter. The same command descriptor that used for the addCommands method.

{
  name: "command-name",
  description: "The help description of command",
  action: function(){ /* The action of the command */ }
}

In future we will add more parameters to configure the command behaviour.

Sorry for the inconvenience caused by this refactoring.