Added allow_None to Scatter3DPlot color_index and size_index
Added allow_None to Scatter3DPlot color_index and size_index

ioam/holoviews,ioam/holoviews,vascotenner/holoviews,basnijholt/holoviews,basnijholt/holoviews,vascotenner/holoviews,vascotenner/holoviews,ioam/holoviews,basnijholt/holoviews