Added Xml Source as an extension.
Added more tests to Xml source, added support of complex selectors.
Added XmlSource to default extensions.
Updated Demo with XmlSource example.
Added XElement formatter,
Added namespace handling,
Updated tests and demo app with collection examples
Moved working with 1st element (if no indexes passed to format) from Source to Formatter.
Merge pull request #21 from tbudurovych/master

Added Xml Source as an extension.