introduce default item
default item is used as base class for all "normal style" efl items.
A "normal style" efl item does have a text,content & extra part.
- The text part is usally used to express some text in the item
- Content part is the *main* content part where the user attention is
- Extra can be used to display some elements that are not directly
getting the attention of the user, it can be seen as something more than
the decoration item field.
Differential Revision: https://phab.enlightenment.org/D9629