Multi threaded

[tbillington]

Multi thread the CLI.

Creates a project discovery thread to look ahead and measure artifact directory size without being blocked on waiting for a user input.

Also moves deletion to another thread so the prompt isn't waiting for filesystem operations before responding to user input.

Should result in a more snappy user experience.

Also moves printing from buffered and with stdout locks to regular println. They were complicating the code for no real world benefit.