XMLTextImportHelper: store parsed RDFa attributes in bookmark map.
XMLTextMarkImportContext::EndElement(): handle RDFa attributes properly.
TextPortionEnumerationTest: add test for bookmark xml:id and RDFa.
SwTxtNode::GetTxtAttrAt: add another mode for getting parent of a meta.
SwXMeta: implement interface css::container::XChild.
SwXMeta::getText(): return this (for consistency with other XTexts).
TextPortionEnumerationTest: add test for XChild and NestedTextContent.
replace SwTxtNode::GetTxtAttr() with methods:
GetTxtAttrAt() handles only those hints where only 1 can be at same position.
GetTxtAttrsAt() handles all hints and returns a vector.
refactor SwXDocumentIndexMark to create InsertTOXMark() method.