Changed default sound settings' values to None

Ignore-this: d787ddbb6bbc59d461e323ef7ccea3c5

darcs-hash:20090318155154-1e3d8-b1a613fcf6cdfc6c809890b6b0c2cdd2b82f3835
Added chat.history_directory global setting

Ignore-this: 3b5a09649ec595728f125b6b70033747

darcs-hash:20090318155412-1e3d8-e9246109b8e6c04b4fae04bfbd4d46357d5e2a68