This class is used to write Ext.data.Model data to the server in an XML format.
The documentRoot property is used to specify the root element in the XML document.
The record option is used to specify the element name for each record that will make
up the XML document.
The name of the root element of the document. Defaults to 'xmlData'.
If there is more than 1 record and the root is not specified, the default document root will still be used
to ensure a valid XML document is created.
Defaults to: "xmlData"