2283: CssBox.HtmlContainer

remove CssBox.HtmlContainer
2284: refactor

1. HtmlElement.TryGetAttribute
2. BoxCreator
2287: code arrangement

refactor and arrange source code
2289
2294: move code ...
2295: move code
2302: move code ...
2303
2304: update sample file
2305: fix BoxSpec Inherit Err
Merge branch 'v1.7dev' into v1.7
2308: Fix BoxSpec
Merge branch 'v1.7dev' into v1.7
2309: Composers Namespace

holds 'Controller' class
2310: BridgeHtmlDocument
2311
2312
2314: refactor, arrange code
2315: refactor
2316