I introduced the property for item a few patches earlier. I do not want
to use a part for this, as i would have to implement the class twice
(Once in the part, once as a selfstanding object).
It would also be kind of weird to have code like:
efl_content_set(efl_part(efl_part("item"), "tab"),bla).

The purpose of this part also got a little bit replaced when the item
was introduced, as this is the central point of data for the tab bar
icon. So need for an additional editition part.