Add setting for changing the notification tone

[bhdouglass]

As the title states I would like to be able to select a tone for the calendar notification.

[hummlbach]

Do want to select from the sounds we already have for the alarms (clock app for example) or do you wish to select a file?

[bhdouglass]

It doesn't matter to me really, and it's probably simpler to just pick from the alarm sounds.

[Danfro]

I added the same functionality on the wish list for notes app.
And as with the alarm sound I would like to be able to set a default sound for new events.