Silent notifications + parameter for it in config

[Elihpmap]

proposition for this enhancement
I feel like this could be cleaner, but it works! If you want me to rework some part of the code don't hesitate!

This adds the bool parameter silent in the config file (which default to true if not precised).
For registering/unregistering action the notif sound is still always played (as I believe those are more important notifications compared to the "opening link" ones)

[nref]

Nice work!

I will later refactor the boolean parameter passed to NotifyService into an enum, to prevent boolean blindness

[Elihpmap]

Thanks for the link I didn't know it was called like that!
Is it considered boolean blindness even though the parameter name is quite explicit though ("isSilent" in this case) ?
Its maybe not obvious at the first look but just looking at the declaration (a simple mouse hover in most IDE I believe) is enough to not be blind anymore x)