Don't forget to figure out that set of interface for widgets
I've realised that the Efl.Container interface is stupid because:
- The name is stupid. Its methods and prefix are "content" not container :)
- It's a bad mix between single slot APIs (content_set/get/unset) and multiple children APIs (iterate, count, ...)
So this should be split into 2 interfaces. One for single slot (used in efl_content_set(efl_part(layout, "part"), subobj)) and the other used in box, table, etc...
I'm just not sure about the naming.