Seperating-Axis GJK and contact information generation algorithm

1. Use Seperating-Axis GJK metioned here: http://mollyrocket.com/849. Also add some kind of margin when using SA-GJK. So we can saftly do a early out, assume that if dot(A, D) < 0, no intersection.
2. If intersection is found, in other words the SA-GJK does generate a simplex which contains the origin. Then we can use the simplex generated from SA-GJK as intial simplex input to EPA to calculate contact information, such as, contact points and normal, penetration depth.

做个笔记，记录下脑袋里边东西…研究了两个星期Collision detection，看得我抓狂。反正我现在的想法就是这样的…那个所谓SA-GJK，作为一个quick test（当然在此之前还需要broad phase collision detection check），确定两个物体在有margin的情况下是否有碰撞。如果有碰撞（没碰撞，当然就没他们啥事儿了），那就需要更进一步确定是否真正的碰撞，如何碰撞的…

虽然SA-GJK只给出boolean，但是我还是得用啊…浪费半天写了一堆代码总不能不用嘛…

继续研究…