allow pre-population of /srv/tftpboot repos in overlay filesystem

Add script to pre-populate /srv/tftpboot/repos in the overlay by
bind-mounting the repository mirrors from the image-building host,
and a corresponding script to umount.
fix repo paths to hardcoded locations (for now)

Later I can adjust this so it works for other people.
add cloud_admin pattern
add cute MOTD
reduce grub prompt time-out to 3 seconds
add terminfo package for better terminal support
add gfxboot-devel, required by Studio's bootsplash.tar

bootsplash.tar has:

  lrwxrwxrwx mongrel/users    0 ./usr/share/gfxboot/themes/studio/Makefile --> ../openSUSE/Makefile

and gfxboot-devel is /usr/share/gfxboot/themes/openSUSE/Makefile
add kernel-default-devel for VirtualBox guest additions

VirtualBox guest additions needs to compile against the kernel headers.
clarify references to non-obvious threshold
don't try to cut corners with RAM allocation for tmpfs
include VirtualBox guest additions in build
add 192.168.124.10 entry to /etc/hosts
the minimum RAM disk size mysteriously went up
add OVF file for admin appliance

This was generated manually in VirtualBox and then exported as OVF.
add metadata.json
metadata.json: change vdisk size to 16GB
import Vagrantfile created via `vagrant package`
automate building of boxes from vmdk built by kiwi
initial stab at a multi-VM Vagrantfile for the whole cloud
add box catalog metadata JSON document

This is as described at http://docs.vagrantup.com/v2/boxes/format.html
and allows us to `vagrant box add cloud-admin3.json` and get the box
with the right version number.