Revert "Retire zpool_id infrastructure"

On managed Debian installations, `/etc/zfs/zdev.conf` is a registered
configuration file, so we must carry this patch until a debconf for converting
it to the new `/etc/zfs/vdev.conf` syntax is implemented.

This reverts commit dbf763b39b232996f0d6bb0022e4446643c18e05.
Prevent manual builds in the DKMS source.

Print an instructive error messsage and exit if the `dkms.conf` file
exists when the userland is configured. (ie: `--with-config=user`)

A non-trivial number of people try to rebuild ZoL from the
`/usr/src/zfs` tree, which is modified to better satisfy Debian
packaging policy and contains only the module sources for DKMS.

Regardless, local installations usually break managed installations,
so this autotools test could be further enhanced to check whether
ZFS has a DKMS registration.
Remove the COPYING file.

Resolve this lintian warning by removing the COPYING file:

	W: zfsutils: extra-license-file usr/share/doc/zfsutils/COPYING
	N:
	N:    All license information should be collected in the debian/copyright
	N:    file. This usually makes it unnecessary for the package to install this
	N:    information in other places as well.
	N:
	N:    Refer to Debian Policy Manual section 12.5 (Copyright information) for
	N:    details.
	N:
	N:    Severity: normal, Certainty: possible
	N:

The COPYING file in this project is a place holder that does not
contain the software license, and it is optional for autotools
because the automake template is "foreign".
Remove all upstream init.d components.

The etc/init.d/ components are redundant because the debian/ overlay
bundles init files according to Debian packaging policy.
Remove the upstream dracut component.

The dracut/ component broke deb systems when it first added to the
upstream ZoL repository, had a near-zero download count when it was
fixed, seems to be unmaintained, and is incompatible with the
dracut-005 package that is currently published in Debian and Ubuntu.
Remove userland dist rules.

The `make dist` rule is used to create the DKMS source package, which
does not contain the userland. (eg: Dist --with-config=kernel only.)

For all userland components in each automake template, delete
instances of EXTRA_DIST and change dist_ to nodist_.