BaseDataAnalysis:plot_color2D: read cmap_levels from plot_dict
BaseDataAnalysis:plot_color2D: read cmap_levels from plot_dict

This commit will allow to specify the number of levels of a colormap or the
levels themself in the plot dict as 'cmap_levels'. They will be handed over to the plotting function pfunc.

QudevETH/PycQED_py3