v7

• Simplifications and a small rework to the immediate renderer's 2d camera api.
  • Now camera_2d_projection_set_to_* helper methods won't mess with the model view matrices.
  • Added camera_2d_reset().
  • Added helper methods to clear each matrix separately.
  • This also fixes a bug where the internal matrices were kept after a reset.
• Added Renderer::camera_3d_reset().
• Added Renderer::camera_3d_camera_transform_matrix_stack_clear() and Renderer::get_camera_3d_model_view_matrix_stack_clear() helper methods.