... as per the design guidance in
https://github.com/gnome-design-team/gnome-mockups-software/blob/master/wireframes/atomic-updates.png

This plugin uses the rpm-ostree DBUS API to handle system updates in
Fedora Atomic installations.

This makes the 'AC power is required' notification appear when trying to
schedule a Dell firmware update on battery power.

Looks like a copy-paste typo.

Search-as-you-type generates lots of these and they are just noise.

When installing or removing, setting the progress on the GsApp works as the UI
is typically wired up to the app that was passed into the plugin loader.
For refresh, or for any other app that was not requested, we have to manually
emit signals using gs_plugin_status_update() so the plugin loader is aware of
the change.

This fixes progress notifications for flatpak on the loading screen. You can
test this using:

rm -rf ~/.local/share/flatpak/repo/refs/remotes/*/appstream/
rm -rf ~/.local/share/flatpak/appstream/
ostree prune --refs-only --depth=1 --repo=~/.local/share/flatpak/repo

...then running a fresh gnome-software to get the loading screen.

This avoids the UI just sitting at 0% complete and then disappearing.

This can take more than 0.5s (especially when dealing with more than one remote)
and can also take some time to timeout if the remote server stops responding.

On slow connections this can take more than 0.5 seconds.

Even on my fast machine the token cache prime takes ~0.7 seconds and thus
triggers the warning.

The initialize(), destroy() and setup() methods are supposed to be fast, as the
loading screen will not be shown while the plugin loader is in the setup phase.

We need to report progress back to the UI somehow, and this is how the other
plugins already do it.

We always want DESKTOP applications listed first.

When there are a lot of applications to update this can take several seconds.
Just keep track of the triggered state to avoid the D-Bus round-trip.

Prevents a warning from coverity.

This is internally implemented having up to 4 GtkListBox objects, each with a
header which is only shown if there are more than one update types.

This moves a lot of functionality out of the GsUpdateList object, and strips it
back to a simple update list without any of the now-unused update-type logic.

This makes the code now match the latest mockups.