* Need a way to run an action when a property changes, but only run it once for the whole. For example, may want to restart apache, but only once despite many config changes being made to satisfy properties. onChange is a poor substitute. * Display of docker container properties is a bit wonky. It always says they are unchanged even when they changed and triggered a reprovision. * Should properties be a tree rather than a list? * Need a way for a dns server host to look at the properties of the other hosts and generate a zone file. For example, mapping openid.kitenet.net to a CNAME to clam.kitenet.net, which is where the docker container for that service is located. Moving containers to a different host, or duplicating a container on multiple hosts would then update DNS too * There is no way for a property of a docker container to require some property be met outside the container. For example, some servers need ntp installed for a good date source. * Docking a container in a host should add to the host any cnames that are assigned to the container. * Either `Ssh.hostKey` should set the sshPubKey attr (which seems hard, as attrs need to be able to be calculated without running any IO code, and here IO is needed along with decrypting the PrivData..), or the public key should not be stored in the PrivData, and instead configured using the attr. Getting the ssh host key into the attr will allow automatically exporting it via DNS (SSHFP record) * Should be possible to generate a metapackage of all packages that properties direct apt to install. Then any other packages can be auto-removed. This would just be a matter of storing the apt-installed packages in an Attr. Although not removing essential and base packages could be problimatic.