Initial patch for Windows only. If this overall approach is agreed upon, I'll start work on the GTK side.
- adds a title and edit box to the Save As dialog for the document title
- document title is populated from the RDF/title element (which are now kept in sync)
- once dialog has been closed for a save, the RDF and title element are updated with the new title
NOTE: The user is not required to fill in the title nor does this patch encourage them in any way other than to add those UI elements to the window. Users can also set the document title in the Document Metadata dialog.