Defaults for sound events - please be less noisy

[Matthias Klose]

One of the things, that almost everybody seems to do when working in a
room shared with other (human beeings) is to turn off the sound at all,
or turn off the most annoying sound events.

These are the "User interface events" for

 - Choose menu item
 - Click on command button
 - Select check box (maybe discussable)

These are observations for larger installations and (of course) personal
 opinions. Looking at other OSes, you see these enabled (WinXX), or
disabled (MacXX).

  Matthias

PS: First submitted as http://bugzilla.ubuntu.com/show_bug.cgi?id=16944