Auto-add user apps

[lwouis]

Add a popup on startup if the user has nothing yet in the app. Propose to add their apps for them.

This means parsing C:/Program Files/ and C:/Program Files(x86) once, then to main sync, check if something new showed up on a timer, or during startup (this can be a pref).

Note that if the user delete an app which was added automatically, we should not add it back on next update. It kind of signify a blacklisting from the user's perspective.