Implement a document factory mechanism. This could be
merged directly into wxXmlDocument.
This means that each XML construct (wxXmlElement,
wxXmlAttribute, and so on) would be factoried from a
method of wxXmlDocument. wxXmlDocument instances
themselves would haveto be factoried from somewhere
as well, perhaps from a static method.
This would allow us to write extensions for specific XML
document formats, like HTML or SVG. Then we could
have specific classes that do type checking and
document validation (without a DTD).
Imagine a subclass of wxXmlElement called
wxHtmlTitleElement that wraps a HTML <title/> element.
