Non-subscribed folders are now hidden.

Todo:

• Check if we show subscribed folders if the parent is hidden (we should)
• Figure out how to include enabling/disabling folders (we have a full listing, so it's basically a matter of an edit mode + checkbox, but this might also be something for an organize view)

editing is probably an item for the next milestone.

Subscribed folders in an unsubscribed parent are currently hidden. We could either solve this at at the QAbstractItemModel level, implementing recursive filtering on top (This feature will only be available directly in QSortFilterProxyModel from qt 5.10 on), or we could implement it in sink (this is non trivial due to the way we recursively query for trees).

Solved for now using a recursive filtering using a krecursivefilterproxymodel

Enabling/Disabling folders is the remainder of this ticket.

See the calendar for a model how this could be implemented.