Added deliteful/ScrollableContainer

Contains:

* A container widget with scrolling capabilities (using delite/Scrollable).
* Intern unit tests.
* Functional tests.

Notes:
* Superseeds https://github.com/ibm-js/deliteful/pull/11.
* Layout troubles of the functional tests on IE (not only IE9 but also IE10) are related with flexbox/LinearLayout issues on IE.