Create a self-contained structure for dracut modules

Create a self-contained structure for dracut modules

All modules now live in a subdirectory /modules.d.  Each module is
self-contained -- it should contain everything that it will install
on the initrd.  All modules must include a script named install, which
will be sourced by dracut.  This script should do the actual file installation
using inst methods.  The moddir variable will point to the full path to the
module dracut is currently working on.

As usual, this patch series applies on top of my previous patch series,
and is available as normalize-modules from http://git.fnordovax.org/dracut.