xml-source should support xml with a default namespace

[Seddryck]

At the moment , the XPath mutation is only supporting an xml without namespace. It should be possible to to use the XPath mutation when the xml is defining a default namespace.

Unfortunately, XPath 1.0 doesn't support default namespace! We'll need to provide a name (prefix to the default) and use it in the XPath.

<xml-source>
  <file>myxml.xml</file>
  <default-namespace-prefix>default</default-namespace-prefix>
  <xpath>
    <from>//default:Parent/default:Child</from>
    <select>default:value</select>
    <from>../default:parentValue</from>
  </xpath>
</xml-source>

[Seddryck]

Beta available in https://ci.appveyor.com/project/Seddryck/nbi/builds/27917260/artifacts or 1.21.0-beta0204