Added framebuffer::AttachNone to distinguish from framebuffer::AttachDefault.  Added viewport settings to scene::renderSink... now a camera can be shared across fbs that are of different sizes.  There are now two kinds of framebuffer::bind... one simple and fast, one that is necessarily slower due to re-setting some state for each side of real time cube maps.  Fixed uninitialized anisotropic setting for scene::texture and added some mip-mapping related predecates.