fix physx simulate->fetchResults; elapsed time sometimes zero

See PxScene.h: "calling simulate() twice without an intervening fetchResults() or fetchResults() twice without an intervening simulate() causes an error condition."
"The parameter [elapsedTime] has to be larger than 0, else the resulting behavior will be undefined."
don't update objects physics if sleeping

physx puts actors to "sleep" when not moving since some time..
use synchronous fetchResults(), fixes the crashing physx?
change default fps to 1/100; enable vsync as default
Merge pull request #13 from lanice/fix_physx_exceptions

Fix physx exceptions
Merge remote-tracking branch 'origin/master' into navigation_enhancement
fix slerp rotation to home orientation
fix moving camera below terrain ground when pitching with mousewheel