UPBGE: Manage per eye projection and modelview camera setting.

Previously there was no difference between the left and right eye when
updating the projection and modelview matrix into the camera, only the
value of these matrices was different.

To help futur work to compute all the camera matrices before rendering,
these matrices are stored in a little struct named View in KX_Camera.
This struct embed the projection and modelveiw matrix but also the frustum
and some flag about the validity of some values.

Because of this new organisation, the user can see in case of stereo the
two projection from python using camera.projectionMatrix[Left/Right].

doc/python_api/rst/bge_types/bge.types.KX_Camera.rst

@@ -97,6 +97,26 @@ base class --- :class:`KX_GameObject`
 
       :type: 4x4 Matrix [[float]]
 
+   .. attribute:: projectionMatrixLeft
+
+      This camera's 4x4 left eye projection matrix.
+
+      .. note::
+
+         This is the identity matrix prior to rendering the first frame (any Python done on frame 1). 
+
+      :type: 4x4 Matrix [[float]]
+
+   .. attribute:: projectionMatrixRight
+
+      This camera's 4x4 right eye projection matrix.
+
+      .. note::
+
+         This is the identity matrix prior to rendering the first frame (any Python done on frame 1). 
+
+      :type: 4x4 Matrix [[float]]
+
    .. attribute:: modelview_matrix
 
       This camera's 4x4 model view matrix. (read-only).