Automatic download only #674

If updates were downloaded automatically that would shorten the time I have to spend applying them, without the risks of automatic updates.

Describe the solution you'd like
Ideally I would like the update manager to download, but not install available updates before notifying me.

Describe alternatives you've considered
Setting up cron-apt to run silently would probably achieve mostly the same effect, but not quite as smoothly, as the update manager doesn't know to check right after cron-apt is done.

Additional context
There could be an additional option for this in Preferences -> Automation:

I suppose this is not as simple as it sounds, with downloads needing root access. But maybe the refresh could check if automatic downloads are enabled, and if so only notify about updates that are at least one day old?