cylc gpanel: fix updating

cylc gpanel will currently fail on update with:
```
  File "/opt/cylc/lib/cylc/gui/gpanel.py", line 205, in update
    status = extract_group_state(status_map.keys(),
AttributeError: 'list' object has no attribute 'keys'
```
This is due to a change in the gsummary-provided data structures at #1245.
I've fixed the gpanel behaviour and changed a few names in gsummary.

@kaday, please review.