Please support color vectorization.

points3d() does not support color vectorization, this feature would be really helpful.

Hacking the vtk object only provide the ability to scale color. For specific use, user need to provide a hacky colormap, which is very cumbersome, could mayavi consider support native color vectorization?

Colormap 256 size also limited the number of colors to be displayed. For a true color point cluster, we also have to convert the true color to 256 color map, which is bad when true color media is supported.