edje: Remove part_object_get from EO

edje: Remove part_object_get from EO

Ooooh. This one might be controversial, as some apps definitely
use the function. But it is so easily abused. For our EO API
we are trying to not expose any internal object, as this prevents
us from making changes to the internal behaviour and structure.
All the features that this API provided should be limited to
read-only access to the internal object. In order to replace
this, we will have to return an Efl.Part object that implements
all those APIs: geometry_get, visibility_get, etc...