This adds a new brush property called "Deformation Target" which controls how the brush deformations is going to affect the mesh data. By default is set to Geometry, which makes the brushes displace the vertices. When set to Cloth Simulation, the deformation of the brush is applied to the cloth solver constraints, so the simulation is responsible to apply the final deformation. This allows to add cloth simulation effects to other sculpt tools with minor modifications to their code. This patch enables Cloth Simulation deformation target for Pose and Boundary brushes, which are tools that are already designed to work in low poly counts and produce large deformations. This allows creating the most common cloth effects, like bending and compressing folds, without relying on collisions. Reviewed By: sergey Differential Revision: https://developer.blender.org/D8578