make python bootstrap automatic
move sudo management to r/common

... and make a file for it in sudoers.yml (todo: add variables to sudoer
template)

**r/matt/meta**: delete r/matt's dependency on r/sshd
**r/common/periodic.yml**: make root alias to $periodic_user
**r/sshd**: enhance template to use sshd_listen_addresses if defined, and
ansible_default_ipv4.address if undefined
update one-time-setup and site to reflect changes