Add support for App with standard AP namespace

[Murad-Awad]

This is a weird one, there are valid docx files that contain an extra xml namespace called ap:, this is a standard openxml thing. In practice I've seen this as a result of taking docx files that are saved in sharepoint. The object is the same as the original App, so we may want to move to an approach that implements XmlRead from scratch to optionally serialize either from ap:Properties or Properties depending on what exists. An example docx file where serialization failed is attached. old_doc_format.docx