Fixed re-entry heat effect.

Drag Center is now automatic. /drag-center off to turn off the marker.

Minor performance improvements.

CoL calculation now occurs on a single thread instead of spawning an individual thread for each update, updates might overall be slightly slower on multiplayer servers but should help simspeed keep up and not clog the server with too many threads.

Eliminated the light grid and replaced with a MyLight. Still experementing with this. Might not work properly at first. Updates to come.

Re-implemented drag reduction at high speed while maintaining heat delta, you will heat up much faster at speed cap and probably mostly disintegrate before you hit the ground with smaller ships.

Updated to prevent conflicts with http://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=837058476