Add Node structure to ref 'node' in result array

The Node structure contains needed info of the referenced node in
the quardtree for fast travesal.

Signed-off-by: plysan <plysab@gmail.com>
Add collision detection demo based on generated terrain

The current algorithm is:
1. A posteriori collision detection
2. Sphere - Plane collision detection

The Object class simulates sphere based on the
CD(collision detection) impl, upon each frame, the object finds
the one triangle plane beneath it in the terrain by traversing Node
structure, and detects if the Object sphere collide with the
triangle plane. If collision is detected, bounce is performed.

Signed-off-by: plysan <plysab@gmail.com>
Add physics simulation demo to viewing position

There is one Object simulated in this patch and Object->position is
bound to the viewing position.

Signed-off-by: plysan <plysab@gmail.com>