Add option manager

[ClementPinard]

Add option manager, similar to pandas option manager

• Add a way to change global option, as environment variables
• Add context manager
• If possible, add function decorator, similar to @torch.no_grad() for more conciseness

First obvious options :

• Verbose, especially the tqdm progress bars
• Widget parameters (which are global cosntants at the moment)
• Bounding box format ? Not sure about this one

[NacerKaciXXII]

Some more option suggestions:

• Persistence (or not) of fiftyone datasets loaded with dataset.to_fiftyone()