- Starting some test for separate pointKdTree to photonKdTree.
  pointKdTree: classic system, search photons inside on 'plane' disc.
  photonKdTree: new system added for SSS, search photons inside on volume space.
- Cleanup some Spanish comments on code and add others.
Clean some unused debug code.
Optimize 'Fdr' function from Egan et al. papers.
Add link to 'distributive property' wikipedia explanation.
Comment for test 'photonSum' function code. Seems unused.
Change '_g' variable to most explicit 'phaseAngle'.
Change generic name 'samples' variable to most explicit 'scatterSamples'.
Same for iterator 'l' to 'liter'
Create variable phTree for use to photonKdTree.
Expand ~photonMap_t() destructor for phTree
Create new updatePhTree function for photonKdTree.
Change updateTree for updatePhTree function in all integrator with SSS support.
Some changes to applied style code