Option to set sound volume

[shamoh]

Chris Chung (https://plus.google.com/107419401392230636938): "But I'd like an option to change the alert noise - particularly the one at the end of the work period. The current one annoys me in a very guttural way."

Timothy Nott (https://plus.google.com/116806966352619947622): "I'd love to be able to control the volume of the notifications."

shamoh: Such option should be persistent.