ENYO-429: Account for RTL directionality in panel handle.

### Issue
When in RTL mode, the panel handle does not appear. This is due to the switch in directionality and the fact that the `margin-left` property is not effective in this case.

### Fix
We add a `margin-right` property that appropriately positions the handle.

Enyo-DCO-1.1-Signed-off-by: Aaron Tam <aaron.tam@lge.com>