Sketcher: ToolSettings Widget - Tool Management

===============================================

Sets the full interface between the DrawSketchHandler and a tool widget available somewhere in the UI.

Signalling is as follows:
1. On activation of the tool, DrawSketchHandler notifies the tool widget.
2. The tool widget retrieves tool information necessary for representation (type of widget, visibility, ...)
3. When the tool widget has created an appropriate widget, it notifies back a widget change.
4. The tool receives the widget handler and can now configure and interact with the widget.

src/Mod/Sketcher/Gui/DrawSketchHandler.cpp

@@ -286,6 +286,27 @@ QString DrawSketchHandler::getCrosshairCursorSVGName() const
     return QString::fromLatin1("None");
 }
 
+std::unique_ptr<QWidget> DrawSketchHandler::createWidget() const
+{
+    return nullptr;
+}
+
+bool DrawSketchHandler::isWidgetVisible() const
+{
+    return false;
+};
+
+QPixmap DrawSketchHandler::getToolIcon() const
+{
+    return QPixmap();
+}
+
+QString DrawSketchHandler::getToolWidgetText() const
+{
+    return QString();
+}
+
+
 void DrawSketchHandler::activate(ViewProviderSketch* vp)
 {
     sketchgui = vp;
@@ -1105,6 +1126,26 @@ void DrawSketchHandler::drawDirectionAtCursor(const Base::Vector2d& position,
     }
 }
 
+std::unique_ptr<QWidget> DrawSketchHandler::createToolWidget() const
+{
+    return createWidget();  // NVI
+}
+
+bool DrawSketchHandler::isToolWidgetVisible() const
+{
+    return isWidgetVisible();  // NVI
+}
+
+QPixmap DrawSketchHandler::getToolWidgetHeaderIcon() const
+{
+    return getToolIcon();
+}
+
+QString DrawSketchHandler::getToolWidgetHeaderText() const
+{
+    return getToolWidgetText();
+}
+
 void DrawSketchHandler::drawEditMarkers(const std::vector<Base::Vector2d>& EditMarkers,
                                         unsigned int augmentationlevel)
 {