This update includes significant refactoring. It moves almost all of the
logic into bash scripts, modeled after the `gci` cluster scripts.

The primary differences between the two are the following:
1. Use of the `/opt/kubernetes` directory over `/home/kubernetes`
2. Support for rkt as a runtime
3. No use of logrotate
4. No use of `/etc/default/`
5. No logic related to noexec mounts or gci-specific firewall-stuff