This patch adds an OpenVDB-based voxel remeshing mode and a metaball-based remeshing mode to the Remesh Modifier.
The Voxel remesh mode is taken from the sculpt-mode-features branch and the metaball remesher from the fracture modifier branch.
For now this is a combined patch since both modes affect the Remesh Modifier.
Putting this up in this form for reference only. I will probably split this into its two modes later.
Edit: i will let this in one mode, since particle and mesh voxelization is totally related, can share the CSG logic and creates less noise in the codebase, aka creating a new modifier is more disruptive.
The CSG logic is also helpful for particle meshing since you can for example cut away unwanted parts of e.g. a meshed sph simulation in order to have a fluid fit into a glass (without simulation overhead)