CMB-1706: Spotlight: Unnatural behavior when focus moves from datagridli...

...st item to paging controls

### Issue:
Focus move between grid list items to paging controls feels not natural.
Focus doesn't move from items to paging down button.
This is because viewport is spotlight "container" and paging controls are outside of container.
Spotlight is find nearest from container to other controls.
But, users don't know about 'container' because it is invisible component.

### Fix:
To make focus move between container to other control more natural,
spotlight should compare position from ex current not container itself.

DCO-1.1-Signed-Off-By: Kunmyon Choi kunmyon.choi@lge.com
Since this will be on the public API, I'd suggest Previous rather than exCurrent which is a bit of an awkward way to say the same thing.