Improve plot functionality (summary)

[natter1]

This issue is meant as a summary issue for all the issues regarding plot functions and for discussions about the big picture (if needed).

• [x] return Plotter object instead of camera position #355
• [x] basic pyvista Theme functionallity #425 (PR #477)
• [ ] discuss/add additional values for MapdlTheme class (numbering, etc.) #425
• [ ] consider plot_nodal... -> plot(solution: NodalSolution) #425
• [x] plot principle stress in combination with a MASS21-element #463
• [x] mapdl.vplot(), the vtk plot header has 'MAPDL Area Plot' instead of 'MAPDL Volume Plot' #467
• [ ] Show deformation (without other nodal information) #348
• [ ] animate_nodal_solution_set for Stresses, Strains #302
• [ ] Interactive 3D-Plots inside Jupyter Notebooks and in simple web applications #214
• [ ] Documentation / wrapping of the VTK interfaces #377
• [ ] title, return_plotter, theme ... are not valid parameters for plotnodal... #494
• [ ] additional parameter plotter for general_plotter #424
• [ ] User defined contour legend controls #577

[akaszynski]

Awesome. Thanks for the list.