focus: item focus moves by geometry.

focus: item focus moves by geometry.

In the widget code, focus origin is added. It can know
the focus movement is originated by which action.
The widgets can choose the item focus moves to last focused item
or geometrically nearby item by focus origin.
In gengrid, focus moves to last focused item if focus origin is
ELM_FOCUS_REVERT. It moves to nearby item if focus origin is from
ELM_FOCUS_UP to ELM_FOCUS_LEFT.

TODO: widgets have items should add the direction feature if it
want the focus to move to nearby item.

@feature