Add actual standoff transforms and desired virtual fit options

Once #254 is merged, there will be two new attributes that we should set appropriately in the DVC example data:

• Protocols will have a VirtualFitOptions that defines the virtual fit spherical search grid as well as the steering range.
• Transducers will have a standoff_transform that defines how the transducer gets displaced by the inserting a standoff under it.

In #254 I have already populated these fields in the DVC example data by filling in some defaults:

• Some default VirtualFitOptions that I made up
• Identity transform for the Transducer.standoff_transform (which means there is no standoff)

Exception: example_transducer.json I added an interesting standoff transform for testing. That can stay as is since it is not a real transducer.

The protocols that need VirtualFitOptions: "neuromod_1p3", "demo_protocol"
The transducers that need standoff_transform: "M2", "curved2_100roc_10gap", "curved2_200roc_10gap"

@peterhollender we can now fill in any actual VirtualFitOptions and standoff_transforms into the DVC database, so let's discuss below how you'd like to do that. You can pull the DVC data and edit it yourself and then push and make PR. Or you can tell us what to add. Or maybe we don't actually care about those transducers and protocols and we should introduce new ones to represent the current efforts?

Wait for #254 to merge, then inspect the DVC example data and example_transducer.json. Review the entries for neuromod_1p3, demo_protocol, M2, curved2_100roc_10gap, and curved2_200roc_10gap, and resolve which actual VirtualFitOptions and standoff_transform values should be recorded. Done means the agreed real values are added to the DVC database and its data change is ready for review.