This change optionally pass constraints down through hierarchy
when measuring. Axis specific dependency information is bubbled
back up (so future multi-pass layout may take further action).
This enables f.ex wrapping textfields to adapt to content a bit
better, but all layout is still done in a single pass (Still WIP
on the layout branch)
List of changes:
-Refactorized virtual scroll methods and introduced virtual GetScrollInfo.
-Added TBScroller to do slow down scroll after panning.
-Added TBScrollerSnapListener for snapped smooth scrolling.
-Added keyboard scroll support in TBScrollContainer and TBSelectList.
-Added possibility to cancel EVENT_TYPE_CLICK for current touch (stopping scroll should not cause click)
-Added flag to TBWidgetEvent to distinguish cursor base pointer events from touch events (Fixes issue #2).
--Pan TBEditField on touch pointer events instead of doing selection scroll.
--Touch events should not result in setting the hover state automatically.
