Added System.Xml.XPath.XmlDocument dependency for UAP10.

Added System.Xml.XPath.XmlDocument dependency for UAP10.

build/nuget/SSH.NET.nuspec

@@ -139,6 +139,7 @@ Fixes:
           </group>
           <group targetFramework="uap10.0">
             <dependency id="SshNet.Security.Cryptography" version="[1.0.0]" />
+            <dependency id="System.Xml.XPath.XmlDocument" version="4.0.0" />
           </group>
         </dependencies>
     </metadata>