Clean up newhost.yml playbook and remove newhost.sh

If you use Vagrant or have PXE setup with Debian preseeding configured,
newhost.sh script is very rarely used, so it will be removed. If needed,
a symlink to 'site.sh' script can be created to run newhost.yml
playbook. That playbook has also been cleaned up and made compatible
with 'site.sh' script; to use password login specify '-k' parameter for
ansible-playbook; to not run on all hosts, specify '-l host' parameter.