physics, config: enable Lennard Jones potential, enable link time optimizations

Quite unstable. Needs tweaks. Lots. And I have _no_, ABSOLUTELY _NO_ idea where to get the coefficients. Where the hell can I find a table of 'em? How does LAMMPS do it? I'll... figure something out. Also, added the option to enable link time optimizations. Link time + resources += lots. Gains? Little to none. But it's the hope that counts. Also reduces size of executable.

I just realized the linking system which I use now is completely unusable. I'd rather go back to the good 'ol system of indecies. Or maybe I'll just abandon this idea of having them saved to arrays. Maybe I'll just use neighbours like the big guys do. Seems nice come to think of it. Lots of optimizations could be made if I switched to neighbours and calculated force only between them. I might put that right after moving each object.