External elm_slideshow: add "string: layout"
External elm_slideshow: add "string: layout"

SVN revision: 50302

tasn/elementary,FlorentRevest/Elementary,FlorentRevest/Elementary,rvandegrift/elementary,rvandegrift/elementary,tasn/elementary,tasn/elementary,rvandegrift/elementary,tasn/elementary,FlorentRevest/Elementary,FlorentRevest/Elementary,tasn/elementary,rvandegrift/elementary