Typos: user-facing and trivial

Several typos and uniformity fixes.
Note: 
*SCL/SimpleDataTypes.py is a upstream stepcode file whose fiz has been submitted upstream and accepted.
*the header of Tools/generateBase/generateMetaModel_Module.xsd  had redundant data. It has been removed. Please double check it.

src/Mod/Assembly/App/Solver/Solver.h

@@ -354,7 +354,7 @@ struct placement_accessor {
     template<typename T>
     void finalize(T& t) {
         //need to do it at once as setting every value step by step would always normalize the rotation and
-        //therefor give a false value
+        //therefore give a false value
         Base::Rotation rot(q0,q1,q2,q3);
         t.setRotation(rot);
         t.setPosition(vec);