Created XmlReferenceDumper
Moved ReferenceDumper to Dumper\YamlReferenceDumper

This is done to make other formats, such as the XmlReferenceDumper
possible. This deprecates the old
Symfony\Component\Config\Definition\ReferenceDumper.
Modified command to support XML dumper
Added and modified tests
Fixed Yaml Dumper

Fixed Yaml scalar prototypes
Marked test incomplete