Sculpt: Invert Scrape to Fill

After adding normal radius, the main use of the Scrape brush is to create flat surfaces with sharp edges. In that case, it does not make sense to have our current "Peaks" version of the brush as its inverted version.
The correct inverted version of Scrape for this use case is the Fill brush. This way you can use this tool to crease both concave and convex sharp edges and to fix the artifacts one version produces with its inverted version.
I think we should merge these two tools into one, but for now, this solution keeps compatibility with the old behavior.

Reviewed By: jbakker

Differential Revision: https://developer.blender.org/D6022

source/blender/makesrna/intern/rna_brush.c

@@ -2060,6 +2060,14 @@ static void rna_def_brush(BlenderRNA *brna)
       prop, "Show Cursor Preview", "Preview the scrape planes in the cursor during the stroke");
   RNA_def_property_update(prop, 0, "rna_Brush_update");
 
+  prop = RNA_def_property(srna, "invert_to_scrape_fill", PROP_BOOLEAN, PROP_NONE);
+  RNA_def_property_boolean_sdna(prop, NULL, "flag", BRUSH_INVERT_TO_SCRAPE_FILL);
+  RNA_def_property_ui_text(prop,
+                           "Invert to Scrape or Fill",
+                           "Use Scrape or Fill tool when inverting this brush instead of "
+                           "inverting its displacement direction");
+  RNA_def_property_update(prop, 0, "rna_Brush_update");
+
   prop = RNA_def_property(srna, "use_pressure_strength", PROP_BOOLEAN, PROP_NONE);
   RNA_def_property_boolean_sdna(prop, NULL, "flag", BRUSH_ALPHA_PRESSURE);
   RNA_def_property_ui_icon(prop, ICON_STYLUS_PRESSURE, 0);