[Review] Request from '' @ 'yast/ycp-killer/messaging-refactoring-2'

Please review the following changes:
  * f547816 Colorize error and warning messages
  * 3b32223 Refactor the Messages module and its usage
  * b7106c4 Use the Messages module for all messages to users
  * 0d35091 Introduce Command#file_action
  * d5e1214 Wrap everything that can fail in commands into an |action|