Raysect

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API Changes:
* VolumeEmitterHomogeneous renamed HomogeneousVolumeEmitter.
* VolumeEmitterInhomogeneous renamed InhomogeneousVolumeEmitter.

Bug Fixes:
* Fixed normalisation bug in FibreOptic observer.

New:
* InhomogeneousVolumeEmitter integrator now pluggable.
* Added cosine weighted cone random vector sampler.
* Added cython utility for determining polygon winding order for n-sided polygons.
* Added triangulate2d function for splitting N-sided polygon into triangles.
* Added lerp and slerp functions to Vector3D.
* Added new utility methods to BoundingBox2D and 3D.
* Added AnisotropicSurfaceEmitter material.
* Added BoundingSphere3D.
* Added MeshPixel. A pixel that uses a mesh as a collecting surface.
* Added TargettedPixel. A pixel that fires additional samples at specific target primitives.
* Added TargettedCCDArray. A CCD that fires additional samples at specific target primitives.
* Added radiance pipelines.
* Added instancing to primitives.
* Added bounding sphere to primitives.
* Tidied up samplers.

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Fixed:
* max_wavelength property of optical ray was broken.

New:
* Diamond demo.

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New:
* Added multiple importance sampling (MIS).
* Added micro-facet based materials.
* Added 2D kd-tree and 2D mesh utilities
* Added parabola primitive.
* Added spherical lens primitives.
* Added render engine workflow model with engines targetting single core and multicore rendering.
* Added StatsBin and StatsArray objects.
* Added a set of utility containers (linked-lists etc..) for use in cython.
* Added metals and coloured emission spectra to the optical library.

Changes:
* Completely re-engineered optical observers.
- New pipeline architecture.
- Adaptive sampling.
- Framework simplifies development of new observers.
* Re-engineered spectral functions (API changes are minimal).
* Renamed num_samples and spectral_samples to bins and spectral_bins.
* Renamed ray_min_depth to ray_extinction_min_depth.
* Optimised the codebase for greater rendering performance.
* Updated lambert material to support MIS.
* Tidied up numerous internal interfaces.

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* initial development releases