Wavefunction simulator should support seeding of bit string sampling

[mhodson-rigetti]

Pre-Request Checklist

• [x] I am running the latest versions of pyQuil and the Forest SDK
• [x] I checked to make sure that this feature has not already been requested

Issue Description

When aiming for repeatable simulation results, the wavefunction simulator itself supports a random seed. However, this is not carried through to the sample_bitstrings method of the Wavefunction class, and so sampled measurements of the wavefunction to not provide seeded repeatability.

Proposed Solution

Recommend the Wavefunction class be updated to accept a random seed, and it to be seeded on creation with something derived from the seed given to the wavefunction simulator.

Additional References

None.

[mhodson-rigetti]

See linked issue #1258 for recommended fix for both these issues.