use mvc for the testbed, update almost all tests, bugfixes, improvements, cleanup

Since I started altering the testbed for better maintainability, I prefered to drop this (tested) large change with a single commit. Some changes below:

Put some globals in their correct place,

Now Testbed uses the MVC pattern (Model-View Controller). This way it becomes better to maintain than using no pattern  in my opinion.

Fixed some bugs in the debug draw interface.

Of course, updated almost all tests because of the differences.

Update script.

examples/testbed/tests/tumbler.h

@@ -21,10 +21,6 @@
 
 #include <testbed/tests/quickhull_test.h>
 
-extern DebugDraw* g_debugDraw;
-extern Camera g_camera;
-extern Settings g_settings;
-
 class Tumbler : public Test
 {
 public:
@@ -35,10 +31,6 @@ public:
 
 	Tumbler()
 	{
-		g_camera.m_center.Set(0.0f, 10.0f, 0.0f);
-		g_camera.m_q.SetIdentity();
-		g_camera.m_zoom = 150.0f;
-
 		{
 			b3BodyDef bd;
 			b3Body* ground = m_world.CreateBody(bd);