Implements #141 normals

Calculate and visualise smoothed normals. The smoothing could be improved to dynamically adjust the smoothing level.

components/renderers/cpp/include/ftl/cuda/normals.hpp

@@ -9,6 +9,7 @@ namespace ftl {
 namespace cuda {
 
 void normals(ftl::cuda::TextureObject<float4> &output,
+        ftl::cuda::TextureObject<float4> &temp,
         ftl::cuda::TextureObject<float4> &input, cudaStream_t stream);
 
 void normal_visualise(ftl::cuda::TextureObject<float4> &norm,