1928: start CssBox Layout Revisit

 start CssBox Layout Revisit
1933
1946: LayoutArgs class

prepare LayoutArgs  class for another Layout technique
1947 AddOffsetCanvasOrigin() to IGraphics
1948: PaintArgs and LayoutArgs

Add ContainingBlock property to PaintArgs and LayoutArgs
Reduce number of call to ContainingBlock property (reduce number of
search)
1950
1951
1957
1960: update Finding Widest Run in CssBox

CssBox.CalculateMinimumWidthAndWidestRun() use ‘line-based’ Run search
style
instead of recursive search.
Merge branch 'v1.7'