Add "addAssertionCharsetMeta"

Corresponds to "addInfoCharsetMeta" from previous project.
Add "addAssertionLangHttp"

Corresponds to "addInfoLangHttp" from previous project.
Add "addAssertionLangAttr"

Corresponds to "addInfoLangAttr" from previous project.
Add "addAssertionLangMeta"

Corresponds to "addInfoLangMeta" from previous project.
Add "addAssertionDirHtml"

Corresponds to "addInfoDirHtml" from previous project. Adds
"htmlOpeningTag" attribute to ParsedDocument.