add an idea about automatically run install-suse-cloud on first boot

Haven't got it working yet though.
move admin node kiwi definition into cloud3-admin/ subdirectory
add new kiwi/README.md
SUSE-CLOUD-3-DEPS now includes HAE packages too
add zerofree
indent to 4 columns for consistency
remove kernel headers if guest additions successfully installed

The kernel headers actually take up quite a bit of disk which we can
potentially save using zerofree.