Add dumpSymbol method to DrawViewSymbol based classes

- this is mainly for debugging output from Arch/Draft

src/Mod/TechDraw/App/DrawViewSymbolPy.xml

@@ -13,6 +13,11 @@
       <Author Licence="LGPL" Name="WandererFan" EMail="wandererfan@gmail.com" />
       <UserDocu>Feature for creating and manipulating Drawing SVG Symbol Views</UserDocu>
     </Documentation>
+    <Methode Name="dumpSymbol">
+      <Documentation>
+        <UserDocu>dumpSymbol(fileSpec) - dump the contents of Symbol to a file</UserDocu>
+      </Documentation>
+    </Methode>
     <CustomAttributes />
   </PythonExport>
 </GenerateModel>