Natml

*INCOMPLETE*

+ Added `Dtype._3d` feature data type for working with 3D models.

+ Added support for specifying `environment` variables when creating endpoints.

+ Fixed import error caused by `PredictorSession` class.

+ Refactored `api.PredictionSession` class to `EndpointPrediction`.
+ Removed `api.PredictorSession` class.

+ Added `demos` CLI menu for managing demos hosted on NatML.
+ Removed `api.Predictor.labels` field.
+ Removed `api.Predictor.normalization` field.
+ Removed `api.Predictor.aspectMode` field.
+ Removed `api.Predictor.audioFormat` field.
+ Removed `api.Predictor.review` method.
+ Removed `api.AudioFormat` data type.
+ Removed `api.Normalization` data type.
+ Removed `api.AspectMode` enumeration.