Add Cell information to API render method

[altavir]

I think the renderer should be available of its cell if possible, so it should be inline fun <reified T : Any> render(noinline renderer: Cell.(T) -> Any) instead of inline fun <reified T : Any> render(noinline renderer: (T) -> Any).

[ileasile]

You have an access to the Notebook instance, and you may simply refer this cell as notebook?.currentCell, why doesn't it suit you?

[altavir]

Did not think about that. I think it would suffice. Still, from API wholeness point of view, it still makes sense. For example, it would be possible to create stand-alone renderers. Of course with currentCell it is just cosmetics.