Don't use canberra-gtk-play to play sounds

[spydon]

Since canberra-gtk-play won't be present on most flavors we shouldn't use this to play sounds, or alternatively only use it when it's present.

There are a few different options:

1. Don't play any sound when canberra-gtk-play isn't present
2. Use something that is present on more systems instead
3. Bundle the welcome sound in assets and use AudioPlayers or similar package to play it
   3.1 Allow configuration of what welcome sound that should be played