The XML serializer currently chooses double or single quotes based upon the content of the attribute (and then encodes the value if needed). This is fine of that's what the user wants, but by default it might be better just to stick with one or the other.
Thus let's provide a configuration choice of double quotes or single quotes for the XML serializer for attribute delimiters, defaulting to double quotes. Provide another flag option for whether the attributes should automatically change (i.e. from double quotes to single quotes or vice-versa) to prevent special encoding if possible (the current behavior); by default we can turn this off for consistency.