fix(*): schedule data containers to specific machines

This PR includes two commits - one which moves *-data containers into new unit files, and one which schedules data containers to new machines. This prevents stateful components from moving hosts and starting with a fresh (and empty) data container. We also gracefully stop Postgres to resolve #638.

See the individual commit messages for details.

TESTING: only unit files and the Makefile were changed, so reprovision Deis and make sure all services are scheduled and started properly:

```console
    $ make uninstall && make run
```

closes #638, #1038