improved the beer-lambert law, the color now also describes the density of the volume
added timer, that measures sp/s, scene building time and rendering time
stop when light was hit, its faster and there is a problem when the ray bounces to many times, a stack overflow can happen(on my machine if the recursion depth is about 4000, although its still possible, the chance should be much less, especially if there is much light...)
added an intersection data structure for more portable and clean intersection(e.g. the intersected point is computed)
Merge branch 'master' into MotionBlur