Performance testing application

[lilleyse]

As we look at #252 and mesh/material pooling it would be helpful to have a performance testing application that lets us measure performance in a repeatable way.

To start the application might

• Load a stage with Cesium World Terrain
• Fly the camera from point A to B
• Record the average FPS, number of tiles loaded, and other useful stats

It would likely be a Kit application similar to cesium.omniverse.app.kit that depends on cesium.omniverse and runs some Python code. Depending on what it needs to do with cesium.omniverse we might need to start exposing a Python API: #12.