NB: the variable 'directory' specifies that the image should be
mounted, when initrd-bootchain feature using.

To provide priority: installer, live, rescue.

Fixed a bug with moving the core in a cycle. This only needs to be
done once.

With this change, we simplify the created initrd image. Kernel
modules and firmware are added by make-Initrd itself. The layer
in Initrd is now one. It also allows you to unifyed configs for
bootloading with propagator and bootchain.
Config files for refind and elilo is creates in mkimage, so have
to copy initrd.img in efi/boot/ with the name full.cz.

This commit is packing a bunch of changes that went
into RELENG-e2k-workstation during its forked
development; it covers three distinct things:

- boot.conf preparation for firmware to load the image;
- fixup of packages common for e2k images;
- major cleanup of obsolete/unused cruft
  (unified kernel and reliable xorg autodetection
  allow us to move away from canned machine-specific
  configurations for the most part).