added an advanced stub to check triangleintersection of a fastKdTree

added reference to a paper in which the trinalge/ray intersection is
explained
edited a comment
caught the method return for trinalge/ray intersection. now it's
evaluated when a triangle is hit.
added a test method to test triangle intersection algorithm

i jsut leave the #define TEST now in the main.cpp, because i always need
to revert the file otherwise.
removed bug, that the triangleiterator is not set in the SAH algorithm
corrected the triangle/ray intersection test