Renamed 'rast' to 'state'
Added Viewport state
Moved TextureInfo and SamplerInfo on Renderer side.
Moved target Plane into the render crate
Implemented Surface (render buffer) interface and implementation
Implemented Viewport, Scissor, and ColorMask states.
Merge pull request #138 from kvark/state

Full framebuffer support for the user, plus missing rasterizer states