[#156] Meaningful names for benchmark scenarios

[NewtonSander]

Reopening #159

#156
To avoid generating merge conflicts on a few open PRs, I won't merge this until some of the larger PRs touching Scenario are merged.

Introduction

Scenarios provide a convenient structure to describe the environment, transducers, and sensors. A collection of preconfigured scenarios are provided with NDK, and can be easily loaded.

The scenario numbering does not correspond to anything meaningful. Instead, it would be helpful for users if we named them with descriptive names, like "3-layer skull model" and "RealisticSkull"

Changes

Rename scenarios:

• Scenario0 -> ScenarioSimple
• Scenario1 -> ScenarioFlatSkull
• Scenario2 -> ScenarioRealisticSkull
• Scenario2Benchmark7 -> ScenarioRealisticSkullCropped
• Scenario3 -> ScenarioUltrasoundPhantom

Behavior

How the new behavior is different from the current behavior, how you tested and how the reviewer can test it.

All unit/integration tests and docs should run as usual. I also searched the project to check for any variable names I missed.