Update survey graphics
Have check_perturbation store perturbations in fn._perturbations
simple_finite_dimensional_extremality_test: Rewrite in terms of generators. Add failing doctest for discontinuous case.
Add simple_extremality_test.sage to tested files
finite_dimensional_extremality_test, extremality_test: Rewrite in terms of generators.
extremality_test: More refactoring
simple_finite_dimensional_extremality_test, extremality_test: Adjust output.
extremality_test: Remove special casing of discrete case
Change find_generic_seed* to generate_generic_seeds* and use it in generate_perturbations_equivariant
generate_generic_seeds_with_completion: Generate all, not just one.
Move call to check_perturbation from generators to callers
fixup
generate_perturbations_simple: Use fraction_field
Populate ._perturbations in extremality_test, not check_perturbation.  Store seed, stab_int, walk_list in perturbation, not in original function.
simple_finite_dimensional_extremality_test: Update documentation
Add (commented out) load of old_walk_and_stability_interval_code.sage
Refactor check_perturbation using new function plot_perturbation_diagram. New function basic_perturbation; use it in plot_perturbation_diagram, plot_old_moves_diagram, plot_completion_diagram.  Update demo