Split out ndstep testing to new script test.py

The code is reused verbatim right now.
test.py: Merge run_ndstep(), run_ndstep_seq()
test.py: Make some parameters easily tweakable via options dict
test.py: To-be-optimized function selected by options['f']
test.py run_ndstep(): De-uglify by caching dim
test.py: Sample optimum and restart points from the same [-4,4] interval

Even closer to the COCO setup.
test.py: Support rich commandline options
test.py: Convert f4 to a class, put all its parameters inside
test.py: Add support for benchmarking on BBOB functions