Added BulletCharacterController.cpp & BulletCharacterController.h stubs.

Useage :
- Link action to key :
Input::LinkActionToKey(ACTION_TYPE Action, struct Key Button);
Input::UnlinkAction(ACTION_TYPE Action);
- Query action directly :
Input::GetStatus(ACTION_TYPE Action);
Input::WasPressed(ACTION_TYPE Action);
Input::WasReleased(ACTION_TYPE Action);

Also works with raw button, but not advised :
Input::GetStatus(Key Button);
Input::WasPressed(Key Button);
Input::WasReleased(Key Button);

Shader::SetUniform override, and implement most of the FBO code for
the Direct3D backend.

projects, we now use Video::SetClearColor, Video::SetClearDepth and
Video::Clear instead, so that the Direct3D equivalents can be called.

Added RayCastResult & a naïve integration for EasyCharacterController.
Enjoy !