examples/c: add C examples
examples/js: add JavaScript examples
Attr.vala: improve stringification
CharacterData.vala: improve documentation
Document.vala: add child management support (YAY), improve documentation
Element.vala: fix bug where stringifyings Elements would show unsynced versions without updated attributes
Entity.vala: doc fix
Node.vala: fix check_wrong_document so documents are handled properly
NodeList.vala: add a warning when appending EntityReferences, noting that we don't (yet) support those
Text.vala: doc fix