Restoring the RandomGenerator state with PyRosetta initialization files (#576)
This quick PR supports:
1. Caching Rosetta's `RandomGenerator` Mersenne Twister (MT19937)
internal state in a PyRosetta initialization file
2. Optionally restoring the MT19937 internal state when initializing
from a PyRosetta initialization file
This enables continuity of the PyRosetta session's MT19937 internal
state from the point at which the PyRosetta initialization file was
written, independent of whether the `RandomGenerator` seed was
explicitly configured.