ENH: added single click selection in plot view
To be merged after vtk/vtk!4531 (merged)
Feature requested in https://discourse.slicer.org/t/plotting-select-point-on-click/3568 video: https://www.dropbox.com/s/vzue6tmchm3vltq/SinglePointSelection.webm?dl=0
@jcfr may you review the VTK PR vtk/vtk!4531 (merged), please?