mkinitramfs: Pass command-line arguments through

Some init programs want to see command-line arguments.  Pass them
through.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Improve default --console settings

This sets iutf8 and propagates rows, cols, and TERM.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
README: Document --console

Signed-off-by: Andy Lutomirski <luto@amacapital.net>