2177
2180: fix em
2181: CssBox.CloseSpec()
2182:refactor
2183:   SpecSetter

rename CssPropSetter to SpecSetter
2184: SpecSetter.SetPropertyValue()

refactor method parameter
2185: CssBox.VerifyDisplayType()
2186: modify BoxSpec ctor

not need WellknownHtmlTagName
2188: CssBox ctor
2189: CssBox use shared BoxSpec

CssBox use shared BoxSpec
with its parent element
2190: CssBox.IsInline

use flags
Merge branch '1.7dev' into v1.7