Replace the "reloadThis" ListModel hack by an actual signal,
works when the subtitle is displayed in more than one place
(e.g. two accounts in the same room connected).
Prevent ListModel items from being deleted on the C++ side (specially
when using .get() from QML and a new ListModel is created)
by setting their parent to the ListModelMap.
- Fix roomList height again, now based on model.count().
All delegates are assumed to be the same height
- Properly update room list when a room is joined or left
- Catch exceptions happening in threads (futures), which previously
passed silently
- Show "Empty room?" as "<i>Empty Room</i>" + gray [?] avatar
To make the models update correctly in QML:
- ListModel and _QtModel merged
- Return a ListModelMap QObject from properties instead of
a DefaultDict → QVariantMap
