Mesh.NumThreads : set/get number of threads
Mesh.MaxNumThreads1D : overrides number of threads for 1D meshing (if != 0 ; 0 by default)
Mesh.MaxNumThreads2D : overrides number of threads for 2D meshing (if != 0 ; 0 by default)
Mesh.MaxNumThreads3D : overrides number of threads for 3D meshing (if != 0 ; 0 by default)