Options can now be selected at
command line without requiring
separate builds of the code

Fixed bug in testbed code

Adjust python api to output slices from
an image so that this can be done from
the command line

Plus additional goodies, such as
- equirectangular camera support
- OpenGL 3.1 support
- more accurate voxel pruning for training
- cleaner GUI

- SIMPLE_RADIAL_FISHEYE
- RADIAL_FISHEYE
- OPENCV_FISHEYE

Can also pass datasets, network configs, or snapshots as positional arguments now.

Makes f-theta and latlong modes more meaningful and paves the way for a future Orthographic mode

Courtesy of Eric Haines

- Snapshot w/ optimizer state no longer crashes
- Versioning of snapshots to prevent crashes upon loading older formats
- Smaller filesize due to saving density grids only up to `m_nerf.max_cascade`
- Even smaller filesize due to saving density grids at half precision

Replaced Reset with First and Last. Initialize list of empty strings for create_empty_nerf_dataset. Python bindings.

- orientable crop volume
- extra python bindings
- better visualization of cameras
- a number of fixed crashes