Refine Swift usage and remove semicolon debris.
General cleanup of NavigationTitlePickerScrollView.

Rename back to *TitleScrollView. 

Add scrollOrientation and box in horizontal paging
behavior.

Minor methods reorganization, including compacting
layout code.

Fixed a minor off-by-1 bug from local subviews
array being copied.

Removed some dead scroll view delegate code
related to the old masking technique.
Minor renaming to NavigationTitleItemType.