Initial work on Broombridge v.0.3

[cgranade]

This draft PR starts work on parsing and serialization logic for a new version of the Broombridge spec, primarily including the ability to specify what symmetries are used to expand lists of two-electron fermionic terms, allowing for the specification of fermionic Hamiltonians that violate eightfold symmetry.

This draft PR includes:

• A new V0_3 class for serializing and deserializing draft Broombridge 0.3 documents.
• A new subcommand export-jw for the qdk-chem tool that allows for exporting a Jordan–Wigner representation of a given input electronic structure problem, without the need to write a C# or Python host.

This draft PR does not yet include:

• Unit or integration tests
• Perf improvements for new serialization / deserialization features
• Deduplication of new code where appropriate

[cgranade]

If you would like to locally test the chemistry command-line tool with these changes:

cd Chemistry/src/Tools
# Convert Broombridge 0.2 to 0.3.
dotnet run -- normalize --format Broombridge path/to/0_2.yaml
# Export JW representation of a fermionic Hamiltonian.
dotnet run -- export-jw --format Broombridge path/to/broombridge.yaml

[anpaz]

/azp run

[azure-pipelines]

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