Allow users to opt out of update notifications

[WesleyBranton]

Currently, updates that have new features will open a new tab when the update is installed. It's a good idea to allow the user to opt out of these, as they may be considered annoying or disruptive by some.

Users who have opted out should be able to see these messages via a "what's new" link.

This could also be a good opportunity to find a better way to onboard new features/settings. Something like a blue notification icon on the browser toolbar button and the options button within the popup.