mkinitramfs: Make configuration more flexible

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
virtme-run: Move mkinitramfs to the end

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Request script executing via initramfs instead of via the kernel command line

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
virtme-run: Split --script into --script-exec and --script-sh

This allows passing arguments to scripts.  It's a bit awkward.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
virtme-init: Turn off virtme-loadmods

It's not necessary, and it slows the boot process.

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