Version 0.2 to version 0.22

- Fixed the x and z coordinate system.  They're mathematically correct. 
- Fixed the projection math.
- I've started to split the header file in smaller ones.  This way it's easer
  to read and understand.
- I've changed the render API.  Now, the camera is defined at "vr_camera" and
  the "vr_define_viewport" parameters.  Note that the API will change a bit
  more in future releases.