elm gen/gengrid/genlist: Changed item class's icon_get to content_get.

elm gen/gengrid/genlist: Changed item class's icon_get to content_get.
Do not limit the swallowed objects to icon. This had to be done before
elm 1.0 and now it's time to break. This will break all applications
which are using gengrid/genlist. Please fix it icon_get -> content_get.

TODO
1. fix theme as well.
2. fix documents.

git-svn-id: svn+ssh://svn.enlightenment.org/var/svn/e/trunk/elementary@64344 7cbeb6ba-43b4-40fd-8cce-4c39aea84d33