Allow operator shelves to contain grouped apps.

r? @diox @ngokevin 

I have a few tests failing locally, but I'm pretty sure it's an ES misconfiguration and not an actual problem. I'll see what CI thinks.
I could be reading that wrong. I have this in my index locally:
```
                    "group_apps": {
                        "393012": 0,
                        "393038": 0,
                        "393047": 0,
                        "393059": 0
                    },
```

Is `0` the grouping index? Would it make more sense to have `0: [<list of ids>]`?