Run different versions of images

check on feasability of restarting a single service with a different version *without* shutting down/snapshotting the chainstate. 

i.e.
```
MINER-1=3.3.0.0.4 MINER-2=3.3.0.0.5 make up
```

then, stop stacks-miner-1, and somehow change the image version to something new, and restart that service. 