BSP fiddling
(WIP) New rendering and kd-tree code

- Makefile: added separate build directory
- main: added callback to initialize world
- trig: added generic select partition axis code
[Fix] Corrects check_kdtree() loop range
(WIP) Rewrite of split_triangle

- Improved numerical stability
- Uses the number of incident vertices pervasively
Bugfix: axis information is now set correctly

openmp pragma
- Added render status printingstatus printing