Refactor to namespaces & explode body params

[jsmith]

• Move data models from foundry/<VERSION>/models to their respective namespace. For example, the V2 dataset models are located in foundry/v2/datasets/models.
• The request body is now passed in as method parameters. For example, rather than creating a branch like this client.datasets.Dataset.Branch.create(dataset_rid, create_branch_request={"name": "develop"}) you would do this client.datasets.Dataset.Branch.create(dataset_rid, name="develop").
• Renamed FoundryV1/V2Client back to FoundryClient
• Removed unused models

[tdeitch]

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