Optimize the SphereMesh and the BoxMesh to share shader, vertexbuffer and indexbuffer.

Add a method AddSphere to the LineManager3D

Create a FullScreenQuad geometry type

Add some static helper functions to the PhysicsHelper: create a sphere, a box, other stuff? + write a test for it

Add function that loads an image from a file to a terrain heightfield. Also add a function to quickly create a model from a terrain heightfield and a way to render it. (plain rendering no geomipmapping stuff or other)

Create an OptimizedDictionary. This is a class that at the same time stores a Dictionary and a List, storing the same items, but allowing both fast search AND for looping.