Adding full rary tree generator

[Morcu]

A new generator has been added as well as it's tests.

[IvanIsCoding]

Thanks for doing this! We're up to a good start, I made comments about mostly about Rust details, I think the generator logic is correct.

[mtreinish]

Thanks for pushing this, I haven't looked at the code in detail yet but from a quick check could you add a release note for the new feature (the procedure is documented here: https://github.com/Qiskit/retworkx/blob/main/CONTRIBUTING.md#release-notes) and also add the function to the api documentation here: https://github.com/Qiskit/retworkx/blob/main/docs/source/api.rst#generators so the docs are rendered

[IvanIsCoding]

More Rust comments, I think we're on a good track. Also: you forgot to run cargo fmt on your code, that is why CI is failling (check the CONTRIBUTING.md file Matthew linked)

[coveralls]

Pull Request Test Coverage Report for Build 1595410260

• 48 of 48 (100.0%) changed or added relevant lines in 1 file are covered.
• 4 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.03%) to 98.45%

---

Files with Coverage Reduction	New Missed Lines	%
retworkx-core/src/min_scored.rs	4	77.78%

Totals
Change from base Build 1594188537:	-0.03%
Covered Lines:	11052
Relevant Lines:	11226

---

💛 - Coveralls

[IvanIsCoding]

LGTM, just some minor details about removing commented out code and a minor docstring detail.

Apart from that, it should be good to go after the rebase 🚀

[IvanIsCoding]

Also, this almost slipped through but we need to add the new generator to the documentation! Check https://github.com/Qiskit/retworkx/pull/471/files#diff-b83b53d2e790a152ae629a3756c2232706f9a9660ed385196b17f63362df2c87R176 for an example, you need to modify api.rst to include your new generator

[IvanIsCoding]

@Morcu I added the missing entry on documentation and your first contribution has been merged! Thanks for writing the generator