to save the world from destruction and spoofin

The watch command uses a buffer instead of the standard output. Using this the watch
command can execute commands and wait the end of the execution to clear and print the buffer.
The watch command also catch cliException and KeyboardInterrupt in order to proceed to clean exit.

The time command now catch the ccli exception and KeyboardInterrupt and
print the execution time before a clean exit.

clearing terminal is now a function of class  Printer.
Command clear, now use it.

Commands loading is now done by crawling commands directory under cccli module.
All command which starts by Commmand_ and which is a son of Command class are candidate.