Allow for audio bell on transfer to be muted

[Dirk Epperson]

This may seem silly, but for those of us who work on audio software, the "ding" on file transfer is quite annoying.

You say "turn down the volume", or "change your default speaker", both reasonable under most circumstances. But when in heavy test mode, which requires audio to be on, the ding on transfers is annoying at best, and invasive at worst.

So, what I am asking for is a "mute audio" selection somewhere in user prefs.

Thanks.