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, closes #1038 
Should this be `@echo` so it's silent? This is the output I'm seeing currently:
```console
gradishar:deis matt$ make run
WARNING: Job(deis-database-data.service) in Registry differs from local Unit(deis-database-data.service)
WARNING: Job(deis-registry-data.service) in Registry differs from local Unit(deis-registry-data.service)
fleetctl --strict-host-key-checking=false load registry/systemd/deis-registry.service logger/systemd/deis-logger.service cache/systemd/deis-cache.service database/systemd/deis-database.service
fleetctl --strict-host-key-checking=false load controller/systemd/*.service
fleetctl --strict-host-key-checking=false load builder/systemd/*.service
echo 

Deis components may take a long time to start the first time they are initialized.
```