Nglui

Fixed

- Fixed an unnecessary import that caused an error.
- Added python package neuroglancer to the requirements so versions with errors or incompatibilities can be avoided.

Added

- **StateBuilder** and **EasyViewer** Substantial refactor, adding basic support for the main Google Neuroglancer branch and the Cave-Explorer/Spelunker deployments coming online with CAVE.
Most functionality should be seamless, with the client checking for version.
Currently, only the [Cave-Explorer](https://ngl.cave-explorer.org/) and [Spelunker](https://spelunker.cave-explorer.org/) deployments are fully supported for this automated version check, as the response depends on a build-specific version.json file.
If no automated version is set or one wants to override any settings, the `target_site` argument can be set to `cave-explorer` or `mainline` for the main Google branch or `seunglab` for the older Seung-lab branch.

Fixed

- **StateBuilder** Recast all layer names as strings to avoid issues with numeric.

Fixed

- **StateBuilder** Fixed various issues with stacking multiple points into a single row.

Added

- **StateBuilder** Adding a helper function for basic line annotation states
- **StateBuilder** Helper functions can take `split_position` argument.

Fixed

- **StateBuilder** Handle None data correctly with mapping sets.