related fixes Various fixes so sculpt_init_tool_override_channels for shift-smooth can replicate the prior behavior: * Brush spacing will now look up brush channel spacing directly for sculpt, instead of relying on copying the channel data into Brush. * Brush spacing code will now use brush channel pressure for sculpt. Fixes broken shift-smooth pen pressure. * The falloff_curve channel is now automatically added (before it was only used internally by command lists, the code was defaulting to the Brush field otherwise). * BrushCurve now has an option for custom curve presets to have negative slopes. * The Falloff panel now puts the type dropbox inside the panel header. * Falloff panel also now uses brush channel data in sculpt mode. * falloff_shape is now a brush channel In a somewhat unrelated change, I also unnested the Brush Settings subpanels. It's been driving me insane for a very, very long time. Much more usable this way.