edje: Edje_Edit - add examples for it's API using for BOX part and items

edje: Edje_Edit - add examples for it's API using for BOX part and items

Summary:
Some little example about how and when edje_edit functions can be applied.
In this example there is a box part with items in edj, and by using edje_edit
program actually changes edj file directly. (adding items,
changing layouts of box, changing params of items, etc).

It is pushed as a reference for people who would like to do there own
Edje editor. Normal application should not use that API.

Reviewers: Hermet, raster, seoz, cedric

Reviewed By: cedric

Subscribers: cedric, reutskiy.v.v

Differential Revision: https://phab.enlightenment.org/D1969

Signed-off-by: Cedric BAIL <cedric@osg.samsung.com>