Remove C++ escaping from *Py.xml templates

Now all escaping required for the C++ code generation is done when the
.cpp/.h files are generated. Previously, only newlines were escaped
automatically. This was a) inconsistent and b) leaked c++ details into
the xml data.
In addition, the escaping is now done in one central place, harmonizing
the three previous implementations.

Pre-existing c++ escape sequences in the XML files have been replaced by
their literal equivalent so that the resulting python doc sting remains
unchanged.

src/Mod/Mesh/App/MeshFeaturePy.xml

@@ -14,7 +14,7 @@
 			<UserDocu>The Mesh::Feature class handles meshes.
 The Mesh.MeshFeature() function is for internal use only and cannot be used to create instances of this class.
 Therefore you must have a reference to a document, e.g. 'd' then you can create an instance with
-d.addObject(\"Mesh::Feature\").
+d.addObject("Mesh::Feature").
 			</UserDocu>
 		</Documentation>
 		<Methode Name="countPoints">