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.
This removes the conflicts between the different parents and also
indicates that this is to be used internally by widgets and should
not be confused with the normal user visible parent.
It is an internal attribute that should not be used by people
not implementing widgets. Marking it as protected signifies it
as such.
Jean-Philippe Andre
Tom Hacohen
Cedric BAIL