algo/ManifoldFactory.cpp is missing about iwengine

[IainWinter]

I really didn't like the double dispatch so currently in the repo there is code here: https://github.com/IainWinter/IwEngine/blob/master/IwEngine/src/physics/Collision/TestCollision.cpp

which calls into: https://github.com/IainWinter/IwEngine/blob/master/IwEngine/include/iw/physics/impl/TestCollision.h

based on a table defined here:

IwEngine/IwEngine/include/iw/physics/impl/TestCollision.h

Line 25 in 3e20528

struct Test_Collision_funcs

This solution removes the need for n^2 functions where n is the number of collider types.

I got the idea for a table of function pointers from page 33 of this valve
document: http://media.steampowered.com/apps/valve/2015/DirkGregorius_Contacts.pdf