'time' command

Implement the UNIX 'time' command with the most common options.
The most important thing is to accuratly tell the total time spent by the command while running. Breaking down the time to user and sys is not reuiqred at this stage of jnode.

Command completetion would be nice. The command name completes on the shell aliases then ideally the subsequent arguments could complete according the the invoked command syntax.

This command would be useful for simple performance testing.