test1.7
Add CssBoxCollection class, optimize Search

1. CssBoxCollection Class: Collect and Manage CssBox Children
benefits:  ontrol Add,Insert,Remove, set parent to CssBox
2. Optimize Collection: Reduce number of times that need to seach
CssBox, in IndexOf or Contains method of List
3. Reorder  MemberItem in CssDisplay Enum : group CssDisplay props that
have Container Property together.
4. CssBox_Corrector.cs : clearify code in
GetPreviousContainingBlockSibling() and  GetPreviousSibling()
No Need for  CssBoxCollection.IndexOf

1. Add PrevSibling Property to CssBox
2. CssBoxCollection manage _prevSibling field of CssBox
3. So No Need for  CssBoxCollection.IndexOf
4.  GetPreviousSibling() and GetPreviousContainingBlockSibling()
could run faster because no need finding index of Box
5. change CssBox's ParentBox to readonly property and add
SetNewParent() to CssBox
Text => Html Dom => CssBox Tree

This update focus on Html Parser.
1. We Parse Html Text source to Html Dom
( with event-driven Lexer and Mini Parser, this still incomplete
and have some errors, it will be corrected in next iterations)
2. from HtmlDom to CssBox tree
(we 'walk' on html dom to generate CssBox tree, then
we can build custom html dom and control custom CssBox
generation)

3. this update is preparation to add Dynamic Html features (with some
scripting!) in near future
clean some code
fix Lexer
Merge branch 'master' into v1.7
update some code layout