Add a scale to the camera move speed based on the scenario size

[bpe2]

Currently, the camera movement speed maxes out at ~0.1 units per frame. This is fine for most scenarios, but at larger sizes (100+ km) this can be a bit limiting.

Introduce some sort of scaling mechanism that adjusts the base speed when loading very large (or potentially very small) scenarios.

See: https://github.com/usnistgov/NetSimulyzer/issues/47