box: add support size hint padding
box: add support size hint padding

Summary: This patch adds suppoting size hint padding for elm_box.

Reviewers: raster, cedric, Hermet

Subscribers: cedric, kimcinoo

Differential Revision: https://phab.enlightenment.org/D3500

Signed-off-by: Cedric BAIL <240633aa59d25638de9800ef43a88ad2e208d24d@osg.samsung.com>

tasn/elementary,tasn/elementary,tasn/elementary,tasn/elementary,tasn/elementary