new interfaces for the CLI and a CLI command
ported CommandLineInterface to new CommandLine interface
removed PrioritizedObersable & PrioritizedObserver as not needed anymore
modified package-info to represent new interfaces
CommandNotFound not needed anymore
moved LoadCommand to new interface
moved StopCommand to new interface
moved UnloadCommand to new interface
extracted exception format string into static final field.

Fixed missing whitespace too.
moved CreateCommand to new interface
added CommandUtil with helpful methods for Command implementations
added forgotten static keyword
moved ChangeDirectoryCommand to new interface
moved CreateDirectoryCommand & ListMemebersCommand to new interface
fixed missing return statement if no disk is loaded.
moved DeleteCommand to new interface
moved DestroyCommand to new interface
moved SizeCommand to new interface
moved QueryCommand to new interface
moved ImportCommand to new interface