* Added the m_rotate_action to qetelementeditor.ui * Adding QAction to qetelementeditor.cpp and connecting it to new slot RotateElementsCommand defined in editorcommands.cpp

* Some types of elements need to specialize the setRotation method in order to behave correctly :
- PartTerminal needs to call setOrientation
- PartLine, PartRectangle and PartPolygon need a different rotation center.

sources/editor/graphicspart/partline.h

@@ -94,6 +94,8 @@ class PartLine : public CustomElementGraphicPart
 		void setFirstEndLength(const qreal &l);
 		qreal secondEndLength() const {return second_length;}
 		void setSecondEndLength(const qreal &l);
+        void setRotation(qreal angle);
+        qreal rotation() const;
 
 	protected:
 		QVariant itemChange(GraphicsItemChange change, const QVariant &value) override;
@@ -124,5 +126,6 @@ class PartLine : public CustomElementGraphicPart
 		int m_vector_index = -1;
 		QPropertyUndoCommand *m_undo_command;
 		QVector<QetGraphicsHandlerItem *> m_handler_vector;
+        qreal m_rot;
 };
 #endif