Updates to mcsolve

- Fixed num_cpus not properly set for multiprocessing.
- Fixed compiler args not recognized by clang.
- Avoid data copy in cy_expect_psi_csr.
- Add ability to reuse seeds [Options(seeds=xxx)].
- Clean up numpy imports.
- Fast reset of scipy zvode integrator and change stepping mode.
seed_reused not used anymore, and not defined here. would be nice with a mentioning of seeds in the docstring here and mybe also in the docstring for mcsolve.