Sculpt: Pose Brush Face Sets FK mode

This Pose Brush origin mode simulates an FK deformation in the entire
model when clicking on the face sets, as they were controls of a fully
rigged character. Combined with the previous Face Sets modes that allow
creating IK chains, the pose brush should now be able to simulate most
of the common rigs deformations.

Reviewed By: sergey

Differential Revision: https://developer.blender.org/D7839

release/scripts/startup/bl_ui/properties_paint_common.py

@@ -623,7 +623,7 @@ def brush_settings(layout, context, brush, popover=False):
             layout.prop(brush, "pose_origin_type")
             layout.prop(brush, "pose_offset")
             layout.prop(brush, "pose_smooth_iterations")
-            if brush.pose_deform_type == 'ROTATE_TWIST':
+            if brush.pose_deform_type == 'ROTATE_TWIST' and brush.pose_origin_type in ('TOPOLOGY','FACE_SETS'):
               layout.prop(brush, "pose_ik_segments")
             layout.prop(brush, "use_pose_ik_anchored")
             layout.separator()