• Added new tasking options: Cilk, Internal, and Debug
• Provides more ways for OSPRay to interact with calling
  application tasking systems
  - Cilk: Use Intel® Cilk™ Plus language extensions (ICC only)
  - Internal: Use hand written OSPRay tasking system
  - Debug: All tasks are run in serial (useful for debugging)
• In most cases, TBB remains the fastest option
• Added support for adaptive accumulation and stopping
• ospRenderFrame now returns an estimation of the variance in
  the rendered image if the framebuffer was created with the
  OSP_FB_VARIANCE channel
• If the renderer parameter varianceThreshold is set,
  progressive refinement concentrates on regions of the image with
  a variance higher than this threshold
• Added support for volumes with voxelType ushort (16-bit unsigned
  integers)
• OSPTexture2D now supports sRGB formats -- actually most images are
  stored in sRGB. As a consequence the API call ospNewTexture2D()
  needed to change to accept the new OSPTextureFormat parameter.
• Similarly, OSPRay's framebuffer types now also distinguishes between
  linear and sRGB 8-bit formats. The new types are OSP_FB_NONE,
  OSP_FB_RGBA8, OSP_FB_SRGBA, and OSP_FB_RGBA32F
• Changed "scivis" renderer parameter defaults
• All shading (AO + shadows) must be explicitly enabled
• OSPRay can now use a newer, pre-installed Embree enabled by the new
  OSPRAY_USE_EXTERNAL_EMBREE CMake option
• New ospcommon library used to separately provide math types and OS
  abstractions for both OSPRay and sample apps
• Removes extra dependencies on internal Embree math types and
  utility functions
• ospray.h header is now C99 compatible
• Removed loaders module, functionality remains inside of
  ospVolumeViewer
• Many miscellaneous cleanups, bugfixes, and improvements:
• Fixed data distributed volume rendering bugs when using less
  blocks than workers
• Fixes to CMake find_package() config
• Fix bug in GhostBlockBrickVolume when using doubles
• Various robustness changes made in CMake to make it easier to
  compile OSPRay