octree traversal rewritten to avoid recursion
reenabled -O3 optimizations (was accidentaly disabled, now it traces even faster! :-))
realtime_bunny: added FPS counter, fixed a bug in ply loader
min3 and max3 templates added to common.h
new virtual Shape::intersect_bbox
implementation of triangle-AABB intersection
octree building updated and simplified with help of this new method
octree made default for Python, it's currently much faster than kd-tree (both building and traversal)