Print formatted result on verbose output

[ranisalt]

As I suggested on a commit

[sharkdp]

Thank you for your contribution. Instead of overloading the meaning of --verbose, what do you think of the following option:

We change the --size-format option to take four (instead of two) parameters:

• decimal
• binary
• plain
• auto

By default, the format is set to auto which automatically chooses either decimal (if we write to a TTY) or plain (if we don't). This way, users can still overwrite the auto format by explicitly choosing decimal, binary, or plain.

[ranisalt]

This is currently above my knowledge of Rust :stuck_out_tongue_closed_eyes:

[sharkdp]

Ok, no worries. I'll take a look at this when I find the time.