[mpl] plot_on_top, temperature cmap, invert cbar

Purpose

meshplotlib:

• added functionality to plot a shape on top of a sliceplot defined by a contour function
• more plot customization options added e.g. titles
• changed colormap for temperatures below 0 °C

propertylib:

• small fix von_mises_stress (for 2D arrays)
• tests are now run for arrays of Scalars and Vectors respectively

Categories

• visualization