v0.6.0

Changes in this release:

• Update to latest ANARI SDK v0.7.0
• New OpenGL based implementation (visgl), built using VISRTX_BUILD_GL_DEVICE=ON
• Added support for sampler in/out transforms
• Fixes for building with OptiX 7.7
• Many extensions synchronized with the v1.0 ANARI specification
• Implemented image backgrounds for all renderers
• Improved robustness for objects that are unknown by emitting better warnings
• Removed custom color map sampler extension in favor of using image1D samplers with transforms (can get equivalent results)
• Denoising is now enabled as a renderer parameter instead of a frame parameter