Ultrasound imaging

[charlesbmi]

Describe the new feature or enhancement

Acoustics physics simulation packages like stride include the ability to do imaging. We would like to implement this pipeline in NDK.

Use-case: help researchers develop state-of-the-art ultrasound imaging, particularly for brain imaging where skull attenuation is a big hurdle.

[charlesbmi]

To-do:

• [x] Port notebooks to new functional API
• [x] Add "recording" to source options
• [x] Update scenario to change material properties