Add various improvements and replaced the default example

* Fix studio initialization: automatically load the default xml without having to go in studio edit.
* Fix children display order in step view. Before, ooyala players was always displayed at the bottom... now the order of the xml is used.
* Replaced the default example with a better one.
I understand why you had to move this here inline - that's not ideal though, and we should revisit this once the fields  callable default is reworked to function without requiring the FIELDS_TO_INIT variable.