[surrogate] make sequential work.

examples/analytical_function/test_analytical_function.py

examples/analytical_function/util/svg_gif.py

src/bayesvalidrox/post_processing/adaptPlot.py

src/bayesvalidrox/post_processing/post_processing.py

src/bayesvalidrox/surrogate_models/sequential_design.py

src/bayesvalidrox/surrogate_models/surrogate_models.py