Sketcher: New Feature: Symmetric tool

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Creates geometry symmetric to the selected one with respect to the last selected point or line.

It does not support the following constraints:

- Angle
- Horiz/vertical distance
- SnellLaw

Horizontal and Vertical (directional) dimensions removed from the the copying process when created
on a single edge (by picking one edge instead of two points), i.e. Constraint involving only one GeoId at "First".

src/Mod/Sketcher/Gui/Workbench.cpp

@@ -245,14 +245,16 @@ inline void SketcherAddWorkbenchTools<Gui::MenuItem>(Gui::MenuItem& consaccel){
         << "Sketcher_SelectRedundantConstraints"
         << "Sketcher_SelectConflictingConstraints"
         << "Sketcher_SelectElementsAssociatedWithConstraints"
-        << "Sketcher_RestoreInternalAlignmentGeometry";
+        << "Sketcher_RestoreInternalAlignmentGeometry" 
+	<< "Sketcher_Symmetry";
 }
 template <>
 inline void SketcherAddWorkbenchTools<Gui::ToolBarItem>(Gui::ToolBarItem& consaccel){
     consaccel << "Sketcher_CloseShape"
         << "Sketcher_ConnectLines"
         << "Sketcher_SelectConstraints"
-        << "Sketcher_RestoreInternalAlignmentGeometry";
+        << "Sketcher_RestoreInternalAlignmentGeometry"
+	<< "Sketcher_Symmetry";
 }
 
 template <typename T>