Update deliteful to match changes between delite 0.3.0 and 0.4.0-alpha.

- Prefer overriding attachedCallback rather than startup (see https://github.com/ibm-js/deliteful/issues/261)
- Rename protected variables (https://github.com/ibm-js/delite/commit/672db9f9ecfb90870fd7914cab2f7f8f835db49f)
- Rename preCreate->preRender, buildRendering->render, postCreate->postRender (https://github.com/ibm-js/delite/commit/a2f7e864a61fc1ff787a9c39c49b5dfcbc142583)
- Rename event handlers (https://github.com/ibm-js/delite/commit/91fb7d379305e39da57adc202fce6f40e5dccdc6)

I think the only tricky part is in `list/PageableList.js`. The `startup`->`attachedCallback` move changed the order of the `computeProperties` and `processCollection` (`computeProperties` was now called before `processCollection`, which lead to `this._collection` being undefined). I tentatively fixed this by adding `_collection` to the `Stateful` properties, so that `computeProperties` is now called again after `processCollection` sets the `_collection` variable. I think a review is needed here, @sbrunot?