updating bitmap sizes now done by graphics context
implementing stacking contexts as separate tree structure
improved hit testing, now use stacking contexts
removed obsolete scrolling code, will be refactored on layer
moved some rendering related code to layer class
removing scrolloffset from element renderer. cant compile
scrollOffset now on layer
added computation of layer matrix before rendering
added font implementation to macro to remove conditional compilation in core
added platform specific timer class to remove conditionnal comp from core
refactored port package
implementing overflow as layer base class
implementing clip rect for rendering
improved overflow implementation + moved geom methods in utils class
added doc
fixing overflow bugs
bug fix in transformations drawing
bug fix on scroll bounds
bug fix for overflow
bug fixes in scrollLeft and scrollTop computation