[TD]SectionView/ComplexSection - preview, direction selection

- add preview/live update to TaskSectionView & TaskComplexSection
- add view direction selector to uis
- use SectionNormal as Direction.  Make Direction read-only
- simplify section line end point calculation
- section group command in toolbar
- make section and complex section icons consistent
- fix compsolid cutting tool
- terminology: single/piecewise to offset/aligned

src/Mod/TechDraw/App/DrawViewPart.h

@@ -154,6 +154,7 @@ public:
     virtual Base::Vector3d getLegacyX(const Base::Vector3d& pt,
                                       const Base::Vector3d& axis,
                                       const bool flip = true)  const;
+    gp_Ax2 localVectorToCS(const Base::Vector3d localUnit) const;
 
 
     bool handleFaces();
@@ -167,6 +168,9 @@ public:
     virtual TopoDS_Shape getSourceShapeFused() const;
     virtual std::vector<TopoDS_Shape> getSourceShape2d() const;
 
+    TopoDS_Shape getShape() const;
+    double getSizeAlongVector(Base::Vector3d alignmentVector);
+
     virtual void postHlrTasks(void);
 
     bool isIso() const;