* src/ColorDialog.cs: fix the contrast setting. * src/StockIcons.cs: add new icons. * src/PhotoView.cs: add desaturate button and sepia button. * src/ColorDialog.cs: add sepia and desaturate buttons. * src/Makefile.am: add new icons to resources. * src/IOChannel.cs: revert warning change. * src/MainWindow.cs: silence warning. * src/IOChannel.cs: get rid of some warnings.