Replace show with a list command

[pawamoy]

The list command lists all downloads, sorts them, limits the result, etc.
It can also be used to quickly see the information about specific downloads in the terminal: it accepts gids or filter patterns.

Maybe do this:

• By default only outputs downloads names.
• Option -l, --long for additional information (--format=long).
• Option -f, --format with choices and custom string.
• Option -s, --sort with choices and custom sort.
• Option -H, --human-readable.