The expected usage is efl_text_set(efl_part(layout, part), text);
Same for text_get.
Also, added an example how to make API easier with providing
efl_text_set/get for the widget itself, in efl_ui_button. Please see
this example.
This touches Edje and also Elementary where part names are used.
This commit blew up in size since now all content part APIs
(get, set, unset) require to use Efl.Part instead.
This is a big refactoring commit, but no logic should
have been changed. Fingers crossed.