import nicer kiwi image building script

This comes from

  https://github.com/SUSE/cloud/blob/master/dev-setup/sles11-sp3/build-image.sh

and has some nice improvements from James Tan, including tmpfs support
and cleaner code.
try a sleep to fix rm: cannot remove ‘/tmp/kiwi-build’: Device or resource busy
fix self-description in build-image.sh
remove old author
remove EULA on first boot
autostart ntp and sshd
the RAM disk needs at least 5GB

... and that's without the software repositories embedded.
mention packer
fill out image-building instructions (WIP)
allow passing parameters to kiwi (e.g. --type)
switch to .vmdk for virtualbox
fix network settings for VirtualBox

First adapter *has* to be NAT:

  https://github.com/mitchellh/vagrant/issues/3619

and AFAICS DHCP is required too.

Therefore we'll set eth1 as 192.168.124.10, and that will
be host-only so that the other VMs can talk to it.
add vagrant user
add vagrant public ssh key
setup sudoers
disable UseDNS in sshd
tweak LESS
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