Gf 61429 Improve getFirstVisibleChild to support horizontal RTL DataList 

Current method does not consider RTL.
when dataList is horizontally reversed in some locale like Arab, this methods always returns index '0' item.
These commits support RTL mode.

Moreover this commits reduce redundant calculation.
Previously, it check every control even though it was included in invisible pages.
To prevent redundant calculation, skip unsuspected page before checking visibility.

Enyo-DCO-1.1-Signed-off-by: David Um david.um@lge.com