HDR output
This release adds support for ray tracing output (file or ndarray) at higher color depths: 16bps and hdr. There is also support for writing and reading hdr images. Another feature that just appeared is a panoramic camera mode for making 360 degree environment maps.
And fixes are:
- correct light emission in volumes
- fix restoring scene global variables from json
- more verbose messaging on initialization problems
- fix camera switching when ray generation program changes.