Kolibri daemon should be restarted after installing updates

[dylanmccall]

When Kolibri is updated, the daemon continues to run in the background until a period of inactivity. This can be problematic, because:

• Using desktop search counts as activity.
• Sometimes, Kolibri updates will result in the frontend having changes that are incompatible with the backend.
• Sometimes, the user will intentionally update Kolibri to a particular version, such as switching from the stable branch to the beta branch, and it is reasonable to expect that stopping the app and starting it again will result in the new version of Kolibri (as in the backend) being started.

To sort this out, we can probably use the org.freedesktop.portal.Flatpak.UpdateMonitor portal API, and / or add some code to the Kolibri frontend that will detect when the backend is a different version and respond accordingly.