2020.0.2

• Added shapes Arrow2D and Arrows2D, SphericGrid, CubicGrid
• completely revised customizable axes=1 type
  • axes can be created for each object independently
• quiver plots, scatter plots, error bands plots
• plotting in spherical coordinates
• Added type '2d' backend to plot static images in notebooks.
  Available backends:

from vtkplotter import *
# embedWindow('2d')
# embedWindow('k3d')
# embedWindow('itk')
# embedWindow('panel')
# embedWindow(False)

• Added wavefront format .OBJ writer