bug fixed : Characters are truncated when HorizontalAlignment.End in

bug fixed : Characters are truncated when HorizontalAlignment.End in
Multi line text on RTL environment.

Recalculate the alignmentOffset only if the line is RTL.

We need to distinguish the RTL variable for alignment and the RTL variable for the text line for position offset.
So the RTL check of the text line is called isLineRTL.

ex)
When running the sample app below, the characters are truncated.

 Stage stage = Stage::GetCurrent();
 stage.SetBackgroundColor( Color::WHITE );

 TextLabel label = TextLabel::New( "Music, Film & TV, Funny, News,
Sports... Access millions of user generaed content and professional
videos from DAILYMOTION website on your SAMSUNG TV.Search, browse and
watch, get a direct access to your own or favorite accounts, watch a
selection of best" );
 label.SetSize( 1250, 600 );
 label.SetParentOrigin(ParentOrigin::TOP_LEFT);
 label.SetAnchorPoint(AnchorPoint::TOP_LEFT);
 label.SetPosition( 100.f, 700.f);
 label.SetProperty( TextLabel::Property::MULTI_LINE, true );
 label.SetProperty(TextLabel::Property::POINT_SIZE, 30);
 label.SetProperty(TextLabel::Property::HORIZONTAL_ALIGNMENT,
"END");
 label.SetProperty(Toolkit::DevelTextLabel::Property::MATCH_SYSTEM_LANGUAGE_DIRECTION,
true );
 label.SetProperty( Actor::Property::LAYOUT_DIRECTION,
LayoutDirection::RIGHT_TO_LEFT );

 stage.Add( label );

Change-Id: I0c1161330de073cef466d8e7119a56a9be606034